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Barium phosphate glasses of the composition (100 − x)Ba(PO3)2–xWO3 with 0–60 mol% WO3 were prepared and studied. Thermal studies of the glasses were carried out with DTA, dilatometry and hot-stage microscopy. Glass transition temperature in this glass series increases with increasing WO3 content from 461 °C (x = 0) to 623 °C (x = 60). Most glasses containing WO3 crystallize on heating within the range of 650–750 °C with the exception of glasses with 20–30 mol% WO3, which are thermally stable. Very high chemical durability of these glasses with dissolution rate of 1.4 × 10−8–6.2 × 10−9 g cm−2 min−1 was also revealed. Crystallization of glasses revealed the existence of a new compound Ba(WO2)2(PO4)2 in the studied compositional series. The compound Ba(WO2)2(PO4)2 possess hexagonal unit cell of dimensions a = 11.5191(1) Å and c = 6.3437(1) Å, and its melting point is 936 °C. Raman spectra of crystallized glasses confirmed the formation of crystalline compound in this glass series and revealed the presence of glass phase in some thermal-treated samples. 31P MAS NMR showed on only one coordination of phosphorus atoms in the Ba(WO2)2(PO4)2 compound. [ABSTRACT FROM AUTHOR]

Abstract The glass to crystal transformation was studied for two glasses with composition 25Na 2 O·50MoO 3.25P 2 O 5 and 25Na 2 O·50WO 3.25P 2 O 5. During the heat treatment process, two crystalline compounds were formed, NaMoO 2 PO 4 and NaWO 2 PO 4 , respectively. Physico-chemical properties of the corresponding glasses and crystals were compared, as well as their Raman and 31P MAS NMR spectra. Differential thermal analysis revealed crystallization peaks at 483 °C for the Mo-containing glass and at 624 °C for the W-containing glass; melting points of crystalline compounds were determined as 695 ± 2 °C for NaMoO 2 PO 4 and 858 ± 2 °C for NaMoO 2 PO 4. Sodium tungstate-phosphate glass has lower solubility in comparison with the sodium molybdate-phosphate glass. The study of the crystallization mechanism showed a prevailing surface nucleation. 31P MAS NMR spectra of the two glasses revealed the same shape and almost the same width, which reflects a similar local environment for P in these glasses. The position of the resonance for W-containing glass at a more negative chemical shift than the Mo-containing one is attributed to the different electrical field strength of W atoms than Mo atoms. 31P MAS NMR spectra of crystals revealed two resonances at +17 and − 0.5 ppm for the Mo glass and at −0.1 and − 1.9 ppm for the W glass, reflecting the presence of two different phosphorus short range environments, in agreement with their crystal structure. Raman spectra showed similarity in structural features for Mo and W glasses and their isomorphic compounds. Splitting of the dominant Raman bands in the crystal spectra reflects a distortion of MoO 6 and WO 6 octahedra. Raman spectra also suggested the breaking of Mo-O-Mo and W-O-W linkages during crystallization. Highlights • Crystallization of 25Na 2 O·50MoO 3.25P 2 O 5 and 25Na 2 O·50WO 3.25P 2 O 5 glasses gives crystals of the same composition. • 31P MAS NMR and Raman spectroscopy enabled to probe environments of P, Mo and W atoms in two glasses and corresponding crystals. • Two different phosphorus sites in isostructural compounds NaMoO 2 PO 4 and NaWO 2 PO 4 are reflected in their 31P MAS NMR spectra. • Similarity in the position of the main Raman band shows the presence of MoO 6 and WO 6 sites both in the glasses and in crystals. • Crystallization of glasses results in the breaking of Mo-O-Mo and W-O-W bonds. [ABSTRACT FROM AUTHOR]

The thermal behavior and crystallization of barium molybdate-phosphate glasses were studied in two compositional series, namely A: (100 − x)Ba(PO3)2–xMoO3 (with x = 0–70 mol%) and B: 50BaO–yMoO3–(50 − y)P2O5 (with y = 0–15 mol% MoO3). Thermal properties were studied with differential thermal analysis and dilatometry. Glass transition temperature increases in series A in the range of 0–40 mol% MoO3 and then decreases with a further increase in MoO3 content, whereas the thermal expansion coefficient in series A reveals a minimum at 50 mol% MoO3. These trends are not observed in series B, where the glass transition temperature increases in the range of 0–15 mol% MoO3 and the thermal expansion coefficient almost does not change. Crystallization of these glasses was studied by X-ray diffraction analysis, Raman and 31P MAS NMR spectroscopy. Large thermal stability of glass with a composition 35BaO–30MoO3–35P2O5 toward crystallization was demonstrated. Crystallization of glasses resulted in the formation of the compound Ba(MoO2)2(PO4)2 in this ternary system. Raman spectroscopy also provided information on the formation of glass-crystalline samples in some studied compositions. [ABSTRACT FROM AUTHOR]

Glasses in the BaO-MoO 3 –P 2 O 5 ternary system were prepared, their basic physical properties measured and their structure studied by Raman and 31 P NMR spectroscopies. A modified glass-forming region in this system under slow cooling of the melt was determined. Four compositional series, namely (50-x/2)BaO-xMoO 3 -(50-x/2)P 2 O 5 (A), 50BaO-yMoO 3 -(50-y)P 2 O 5 (B), 20BaO-zMoO 3 -(80-z)P 2 O 5 (C) and (70-u)BaO-uMoO 3 -30P 2 O 5 (D) were chosen for a discussion on changes of the structure and properties of the studied glasses. The glass transition temperature revealed a maximum in series A at x = 40 mol% MoO 3 and in series C at z = 50 mol% MoO 3 , whereas monotonous increase of T g in the series B and monotonous decrease in the series D was observed. 31 P MAS NMR spectra of the glasses revealed depolymerization of the phosphate network, due to the incorporation of molybdate units, and isolated PO 4 groups were identified in glasses with high MoO 3 content. Fitting the NMR spectra provided compositional dependences of phosphate units Q n . On the Raman spectra of glasses with low MoO 3 content, a strong vibrational band at 940–944 cm − 1 , with a shoulder at ~ 910 cm − 1 , dominated the spectra, which was assigned to the vibration of terminal oxygen atoms in molybdate structural units (M O – and M O). In glasses with high MoO 3 content, a broad band at ~ 854 cm − 1 , ascribed to Mo O Mo bonds, showed on the formation of octahedral clusters composed of MoO 6 units in the structure of these glasses. [ABSTRACT FROM AUTHOR]

Study of the glass to crystal transformation was realized for two ternary compounds belonging to the glass-forming region of the BaO Nb 2 O 5 P 2 O 5 system: Ba 3 Nb 2 (PO 4 ) 4 O 2 with 16.66 mol% Nb 2 O 5 (glass composition 3BaO.1Nb 2 O 5 .2P 2 O 5 ) and BaNb 2 P 2 O 11 with 33.33 mol% Nb 2 O 5 (glass composition 1BaO.1Nb 2 O 5 .1P 2 O 5 ). Physico-chemical properties of the corresponding glasses and crystals were compared, as well as their Raman, 31 P and 93 Nb NMR spectra. The density of polycrystalline samples is higher by 0.24–0.25 g cm −3 than the density of the corresponding glasses. 31 P MAS NMR spectra show a close similarity of phosphorus environments in glasses and the corresponding crystalline samples. High-field (18.8T) NMR and 93 Nb decoupling were necessary to obtain enough resolution on 31 P NMR spectra to separate the 2 different short range environments of phosphorus atoms in Ba 3 Nb 2 (PO 4 ) 4 O 2 . Static 93 Nb NMR spectra showed the presence of distorted NbO 6 octahedra both in the 3BaO.1Nb 2 O 5 .2P 2 O 5 glass and the corresponding Ba 3 Nb 2 (PO 4 ) 4 O 2 crystals, while the presence of more symmetric NbO 6 octahedra was detected in the BaNb 2 P 2 O 11 compound, which is in accordance with the crystalline structures. Raman and NMR spectra showed similar short-range structural features in glasses and polycrystalline samples, whereas Raman spectra could detect some differences in the medium-range order of the BaO.Nb 2 O 5 .P 2 O 5 glass and the corresponding BaNb 2 P 2 O 11 crystal. [ABSTRACT FROM AUTHOR]

Phosphate glasses of the ternary system BaO-Nb 2 O 5 -P 2 O 5 were studied in two compositional series, namely 40BaO-xNb 2 O 5 -(60-x)P 2 O 5 (series A), with x = 0–40 mol% Nb 2 O 5 , and yBaO-20Nb 2 O 5 -(80-y)P 2 O 5 (series B), with y = 20–60 mol% BaO. Nine homogeneous glassy samples were prepared altogether in both series, and their basic physical properties (density, molar volume, glass transition temperature, dilatometric softening temperature and thermal expansion coefficient) were determined. The chemical durability of the Nb 2 O 5 -containing glasses is high and the dissolution rate at 80 °C is lower than 4–5 × 10 − 8 g cm − 2 min − 1 . The glass transition temperature of the glasses in series A increased significantly with increasing Nb 2 O 5 content from 324 to 727 °C, whereas in the series B with increasing BaO content, T g increased within the range 620–725 °C. The index of refraction increased more steeply in glass series A with increasing Nb 2 O 5 content than in the glass series B. According to the Raman spectra in the glass series A, at low Nb 2 O 5 content niobium forms isolated octahedra NbO 6 incorporated in the glass network, but when Nb 2 O 5 content increases, these octahedra are linked into chains and further into three-dimensional clusters. In glass series B, NbO 6 octahedra form only Nb O Nb O chains connecting NbO 6 octahedra. NbO 6 octahedra clustering is reflected also in the 31 P MAS NMR spectra of BaO-Nb 2 O 5 -P 2 O 5 glasses showing on a non-monotonous transformation of phosphate units in the direction Q 3 → Q 2 → Q 1 → Q 0 , both with increasing Nb 2 O 5 content in the first A series and BaO content in the second B series. [ABSTRACT FROM AUTHOR]

Glasses of the ternary system BaO B 2 O 3 P 2 O 5 were prepared and studied in broad concentration limits covering the whole vitrification domain: 20–50 mol% BaO, 0–40 mol% B 2 O 3 and 20–60 mol% P 2 O 5 . Their structure was studied with combinations of Raman spectroscopy, 31 P MAS NMR spectroscopy and 11 B MAS NMR spectroscopy. The obtained results are discussed in several compositional lines A: (100-x)Ba(PO 3 ) 2 xB 2 O 3 , B: 40BaO yB 2 O 3 (60-y)P 2 O 5 , C: (50-z)BaO zB 2 O 3 50P 2 O 5 , D: (60-w)BaO wB 2 O 3 40P 2 O 5 and E: uBaO 40B 2 O 3 (60-u)P 2 O 5 . Boron oxide incorporates into the phosphate network in the form of BO 4 and BO 3 groups and increases their glass transition temperature. Nevertheless, the increase in T g is only steep within the region of 0–20 mol% B 2 O 3 reaching a maximum at the glasses with ∼30 mol% B 2 O 3 . In the lines A, B and E a decrease in the P 2 O 5 and an increase of B 2 O 3 content results in the shortening of phosphate chains with decreasing P 2 O 5 content; these changes are most pronounced in line B with a constant BaO content. In lines C and D with a constant P 2 O 5 content a decrease in the BaO content results, in contrast, in the reverse transformation of phosphate structural units in the direction Q 1 → Q 2 → Q 3 as detected from Raman spectra and 31 P MAS NMR spectra. 11 B MAS NMR spectra revealed that only BO 4 units are present in the glasses with 0–20 mol% B 2 O 3 . In the glasses of the E series the fraction of BO 3 units increases with a decreasing P 2 O 5 content. By the decomposition of the 11 B MAS NMR spectra it is possible to estimate the fractions of basic structural units formed by boron - B(OP) 3 O, B(OP) 2 O 2 and BO 3 in all the glasses of the glass forming region. [ABSTRACT FROM AUTHOR]

Borophosphate glasses of the BaO-BO-PO ternary system were prepared and studied within the large glass-forming region of the system. Fourteen investigated glass samples of barium borophosphate glasses were discussed for a comparison of the compositional trends in their properties in four compositional series such as A: (100 − x)Ba(PO)- xBO, B: 40BaO- yBO-(60 − y)PO, C: (50 − z)BaO- zBO-50PO, and D: (60 − w)BaO- wBO-40PO. Changes in glass density and molar volume primarily depend on the BaO content in the glasses. The thermal properties were studied with a differential thermal analysis, hot-stage microscopy, and dilatometry. Glass transition temperature increases with a rising BO content most rapidly in the glass series A and B. It reaches its maximum in these series for the glasses containing 20-30 mol%, where the glass network represents a 3D structure interlinked with P-O-B, P-O-P, and B-O-B bridges. The thermal expansion coefficient decreases, in contrast, with the increasing BO content in these ternary glasses as well as their chemical durability. The crystallization of these glasses, in the samples with a low BO content, results in the formation of barium metaphosphate BaPO. Certain crystallized samples also contain a small amount of BPO, and diffraction lines of ternary compounds BaBPO and BaB(PO) were revealed in a number of samples. A new compound of the composition BaBPO was identified in the crystallized glass 50BaO-10BO-40PO. [ABSTRACT FROM AUTHOR]

Phosphate glasses containing a high amount of niobium oxide exhibit non-linear optical properties which make them attractive for various optical devices. This contribution is devoted to the investigation of glasses of the series (100 − x)[0.5BaO–0.1B 2 O 3 –0.4P 2 O 5 ]–xNb 2 O 5 with x = 0–45 and 80[0.5BaO–yB 2 O 3 –(0.5 − y)P 2 O 5 ]–20Nb 2 O 5 with y = 0–0.25. The basic characteristic parameters of the prepared glasses were determined. The index of refraction of these glasses increases substantially with increasing Nb 2 O 5 content from 1.620 to 2.007 and the glass transition temperature increases within the range of 551–704 °C. The glass structure was investigated by 31 P, 11 B and 93 Nb NMR, and Raman spectroscopies. Raman spectra revealed that at low Nb 2 O 5 content a strong vibrational band of isolated NbO 6 octahedra dominates the spectra. New bands appear in the Raman spectra in the glasses with 30 mol% of Nb 2 O 5 that were assigned to vibrations of Nb–O–Nb bonds interconnecting NbO 6 octahedra. 11 B MAS NMR spectra reveal the dominant role of BO 4 units in the glass structure. 11 B MAS NMR spectra revealed that with increasing Nb 2 O 5 content new resonances of BO 4 units appear in the spectra due to the replacement of B–O–P bonds by B–O–Nb and B–O–B bonds. With an increasing Nb 2 O 5 content, part of the BO 4 units is also converted to BO 3 units. 93 Nb MAS NMR spectra primarily reflect changes in the length of Nb–O bonds in the NbO 6 octahedra manifested in a decreasing asymmetry of the octahedra with increasing Nb 2 O 5 content and the formation of niobate clusters. Niobo-borophosphate glasses reveal very high chemical durability as well as high glass transition temperatures due to the replacement of weaker P–O bonds with stronger Nb–O bonds. [ABSTRACT FROM AUTHOR]

The effect of WO 3 on the properties and structure of PbO–B 2 O 3 –P 2 O 5 –WO 3 quaternary system was studied. Glasses containing up to 60 mol% WO 3 were prepared and the variation of several physical properties was determined with respect to chemical composition in a broad compositional range. Chemical durability of WO 3 -containing glasses is very high and their thermal stability as well. Glass transition temperature increases with increasing WO 3 content up to 566 °C. Glass structure was studied by Raman spectroscopy and 31 P and 11 B MAS NMR spectroscopy. NMR spectroscopy reveals the formation of B–O–W linkages and also the existence of tetrahedral BO 4 units and trigonal units BO 3 in the glass structure. With increasing WO 3 content in the glasses, the number of starting tetrahedral B(OP) 3 O units decreases and B–O–P bridges are replaced gradually by B–O–W and B–O–B bridges, while the number of BO 3 units increases. Raman spectra of the studied glasses possess a doublet of strong vibrational bands in the range at 800–1000 cm −1 , assigned to vibrations of W–O − and W O bonds in tungstate structural units. In glasses with a higher WO 3 content WO 6 octahedra form tungstate clusters interconnected by W–O–W bridges as reflected in the Raman spectra. The formation of strong P–O–W and B–O–W linkages in the studied glasses explains high chemical durability of the glasses and the observed increase in the glass transition temperature. [ABSTRACT FROM AUTHOR]

The effect of indium oxide on the structure and properties of zinc phosphate and zinc borophosphate glasses has been investigated in the series (50− x)ZnO-xInO-50PO and 30ZnO-(20− x)BO-xInO-50PO with x = 0-20 mol% InO in both series. Their physical properties were measured, and their structure was studied by Raman and NMR spectroscopy. Glass transition temperature in the phosphate glass series increases with increasing InO content as well as their chemical durability. The observed changes in the P MAS NMR spectra with increasing InO content revealed the depolymerization of phosphate chains due to the replacement of ZnO by InO resulting in an increase in the O/ P ratio in the glass structure. B MAS NMR spectra revealed the presence of BO units in the glass structure in the borophosphate glass series; these spectra give no evidence for the formation of B-O-In bonds. Their glass transition temperature slightly decreases with increasing InO content. The values of the molar volume in these glasses do not change substantially when BO is replaced by InO. This can be ascribed not only to differences in boron (BO) and indium (InO) coordination, but also to a higher ionicity of In···O bonds in comparison with B-O bonds. The obtained data resulted in the conclusion that indium oxide behaves as a modifying oxide in both glasses. [ABSTRACT FROM AUTHOR]

Lead borophosphate glasses formulated with TeO2 were prepared and studied in the compositional series (1 - x)[50PbO-10B2 O3 - 40P2O5]-xTeO2 with x = 0-0.7 and glasses with 20 and 60 mol% TeO2 with also the B2 O3/P2O5 ratio of 5/45 and 15/35. Structural studies by 31P and 11B MAS NMR and Raman spectroscopies revealed the formation of P-O-Te bonds. The addition of TeO2 resulted in the depolymerisation of phosphate chains as revealed from the 31P MAS NMR spectra. The addition of TeO2 to the parent lead borophosphate glass resulted in the formation of B-O-Te bonds and B(OP)4 - n(OTe)n mixed structural units, the number of which increases with increasing TeO2 content and also with the increasing B2 O3/P2 O5 ratio in the glasses. Only a small number of BO3 units (less than 4%) are formed in glasses with a higher TeO2 content and at a high B2O3/P2 O5 ratio. The Raman spectra also indicated that at low TeO2 concentrations, tellurium atoms form preferentially TeO3 structural units, whereas at higher TeO2 content, TeO4 units are predominant in the glass network. With the replacement of P2O5 by B2 O3 in the studied glasses, TeO4 units are converted into TeO3 units as the number of oxygen atoms in the glass decreases when the B2 O3/ P2 O5 ratio increases. [ABSTRACT FROM AUTHOR]

The crystallization of PbO–WO3–P2O5 ternary glasses was studied in three compositional series of (100−x)[0.5PbO–0.5P2O5]–xWO3 glasses (A series), 50PbO–(50−y)P2O5–yWO3 glasses (B series) and (50−z)PbO–50P2O5–zWO3 glasses (C series) beginning with Pb(PO3)2. The crystallization products of the annealed glass powders were evaluated using X-ray diffraction and Raman spectroscopy. The results of the X-ray diffraction analysis of the crystallized glasses revealed the formation of several crystalline phosphate compounds and in the samples with a high WO3 content also the formation of a new crystalline compound of Pb(WO2)2(PO4)2 in series A and B. From the obtained diffraction pattern, the hexagonal cell parameters were calculated as a =11.3531(1) Å and c =6.3168(1) Å. The surface mechanism of crystallization dominates the crystallization process of the glass into the Pb(WO2)2(PO4)2 compound as evaluated using Day's method. Raman spectra of the crystallized samples confirmed the results of the X-ray diffraction measurements and provided information on the thermal stability of the glasses and formation of the glass-crystalline phases by the annealing of glass samples. [ABSTRACT FROM AUTHOR]

• Glass-forming region in the system K 2 O-Nb 2 O 5 -P 2 O 5 was determined. • Glass structure and properties were studied in three compositional series. • Phase separation and crystallization limit glass-forming region. • Clustering of niobate octahedra results in the formation of potassium niobate crystals. Glasses of the ternary system K 2 O-Nb 2 O 5 -P 2 O 5 were studied in three compositional series (60-x)K 2 O-xNb 2 O 5 -40P 2 O 5 (series A) with 10–40 mol% Nb 2 O 5 , 40K 2 O-yNb 2 O 5 -(60-y)P 2 O 5 (series B) with 10–30 mol% Nb 2 O 5 and zK 2 O-20Nb 2 O 5 -(80- z)P 2 O 5 (series C) with 20–50 mol% K 2 O. The basic physical parameters of glasses were also determined. Almost all the glasses were colourless, only two glasses with a higher Nb 2 O 5 content were blue coloured due to the presence of a small amount of Nb4+ ions. The glass transition temperature in the series A and B increases with increasing Nb 2 O 5 content, whereas in series C it increases only slightly. The highest value of 757 °C was found for the glass 20K 2 O-40Nb 2 O 5 -40P 2 O 5 from the A series. The refraction index only increases significantly in the glasses of the series A and B with increasing Nb 2 O 5 content; glass 20K 2 O-40Nb 2 O 5 -40P 2 O 5 from the series A had the highest value of 1.809 at 587.6 nm. The glass structure was evaluated from an analysis of their 31P MAS NMR and Raman spectra. The efficiency of Raman scattering by NbO 6 units is higher than that of PO 4 units, which results in the suppression of phosphate vibrational bands in the Raman spectra of glasses with a higher Nb 2 O 5 content. In the glasses with 30–40 mol% Nb 2 O 5, Raman spectra showed on the formation of chains Nb-O-Nb interconnecting NbO 6 octahedra and even on the formation of 3D niobate clusters. Samples containing less than 30 mol% P 2 O 5 revealed a tendency to form glass-crystalline materials containing potassium niobate crystals. Their crystalline structure was not identified, but according to their Raman spectra, they contain NbO 6 octahedra similar to those in KNbO 3. [ABSTRACT FROM AUTHOR]

Abstract: Zinc borophosphate glasses doped with TeO2 with different B2O3/P2O5 ratio were prepared, their basic properties were determined and their structure was studied by 11B MAS NMR and Raman spectroscopies. Structural studies were devoted to the investigation of changes in boron coordination in the dependence on changes in TeO2 content and in B2O3/P2O5 ratio in the borophosphate glasses. A special attention was devoted to the formation of mixed structural units B(OP)4−n (OTe) n in the studied borophosphate glasses, where by the deconvolution of 11B MAS NMR spectra quantitative data on the number of BO3 and B(OP)4−n (OTe) n mixed structural units were obtained. Raman spectra showed shortening of phosphate chains both with increasing TeO2 and B2O3 content. Raman spectra also showed that with the replacement of P2O5 by B2O3 in the studied glasses TeO4 units are replaced by TeO3 units as the number of oxygen atoms in the glass decreases when the B2O3/P2O5 ratio increases. [Copyright &y& Elsevier]

Thermal properties and crystallization of glasses from PbO-MoO-PO ternary system were studied in three compositional series (100 − x)[0.5PbO-0.5PO]- xMoO (A), 50PbO- yMoO-(50 − y)PO (B), and (50 − z)PbO- zMoO-50PO (C). Glass transition temperature, crystallization temperature, coefficient of thermal expansion, and dilatation softening temperature of the studied glasses were determined by differential thermal analysis and dilatometry. Crystallization products of annealed glass samples were investigated by X-ray diffraction and Raman spectroscopy. X-ray diffraction analysis of crystallized glasses revealed the formation of PbPO, PbPO, and PbMoO in the samples of the B series. In the series A and C in the samples with a high MoO content, crystalline compounds of Pb(MoO)(PO) and (MoO)(PO), respectively, were identified. Raman spectra of crystalline samples confirmed the results of X-ray diffraction measurements and provided also information on thermal stability of glasses and formation of glass-crystalline phases in the studied glass series. [ABSTRACT FROM AUTHOR]

Abstract: Glasses in the ternary system PbO–MoO3–P2O5 were prepared in three compositional series (100−x)[0.5PbO–0.5P2O5]–xMoO3 (A), 50PbO–yMoO3–(50−y)P2O5 (B) and (50−z)PbO–xMoO3–50P2O5 (C) and their structure was studied by Raman and 31P NMR spectroscopies. In the compositional series (100−x)[0.5PbO–0.5P2O5]–xMoO3 homogeneous glasses were prepared in the concentration region of 0–70mol% MoO3. Their glass transition temperature increases with increasing MoO3 content having a maximum at x=50mol% MoO3. 31P MAS NMR spectra reveal that in the glass series (A) the incorporation of MoO3 results in the shortening of phosphate chains and gradual transformation Q2 units into Q2 and Q0 units, prevailing in glasses with a high MoO3 content. Octahedral structural units MoO6 dominate in most glass compositions and they are present also in the structure of Pb(MoO2)2(PO4)2 compound corresponding to the glass composition 50Pb(PO3)2–50MoO3. The analysis of Raman spectra of glasses of the (B) series with a high MoO3 content showed the transformation of octahedral MoO6 units into tetrahedral MoO4 units. [Copyright &y& Elsevier]

Abstract: Glasses in the ternary system ZnO–MoO3–P2O5 were studied. The determined glass-forming region is very large and covers the concentration range from pure P2O5 up to the glass compositions with only 20mol% P2O5 and 70mol% MoO3. Structure of these glasses was analyzed in four compositional series containing 50mol% of P2O5 in the series of (50− t)ZnO–tMoO3–50P2O5, 10mol% of ZnO in the series of 10ZnO–yMoO3–(90− y)P2O5 and 20mol% MoO3 in the series of zZnO–20MoO3–(80− z)P2O5. The fourth series contained equimolar ratio of ZnO/P2O5 and its composition was (100− x)[0.5ZnO–0.5P2O5]–xMoO3. Basic structural units in this ternary system were identified in specific compositional regions using Raman and 31P MAS NMR spectroscopy. By the deconvolution of NMR spectra compositional dependences of Q n units were obtained. The presence of isolated MoO6 octahedra was detected in the glass with 70mol% P2O5. In the MoO3-rich and ZnO-rich region clustering of MoO6 octahedra was observed, but the formation of Mo–O–Mo bonds was found already in the P2O5-rich glasses containing 60mol% P2O5. Molybdate structural units are preferentially bonded to non-bridging oxygen atoms of PO4 units and P–O–Mo bonds do not tend to replace P–O–P bonds. [ABSTRACT FROM AUTHOR]

Abstract: ZnO–B2O3–P2O5 glasses doped with MoO3 were investigated in the series (100−x)[0.5ZnO–0.1B2O3–0.4P2O5]–xMoO3, where bulk glasses were obtained by slow cooling in air within the compositional region of 0⩽ x ⩽60mol% MoO3. The incorporation of MoO3 into the parent zinc borophosphate glass results in a weakening of bond strength in the structural network, which induces a decrease in chemical durability and glass transition temperature. Raman spectra reflect the incorporation of molybdate groups into the glass network of the studied glasses by the presence of the polarized vibrational band at ≈976cm−1 ascribed to the MO x symmetric stretching vibrations and the depolarized band at ≈878cm−1 ascribed to the Mo–O–Mo stretching vibration. The incorporation of molybdate units into the glass network results in the depolymerization of phosphate chains and the formation of P–O–Mo bonds, as reflected in Raman and 31P NMR spectra. According to the 11B MAS NMR spectra, tetrahedral B(OP)4− x (OMo) x units are formed in the glasses, whereas only a small amount of BO4 units is converted to BO3 units in the MoO3-rich glasses. [Copyright &y& Elsevier]

Abstract: Bulk glasses of the series (1− x)[0.5K2O–0.1B2O3–0.4P2O5]–xNb2O5 with x =0–45.7mol% Nb2O5 were prepared by slow cooling in air and investigated by Raman, 31P, and 11B MAS NMR spectroscopy. The incorporation of Nb2O5 into the parent borophosphate glass results in a substantial increase in the glass transition temperature and chemical durability of glasses. Raman spectra showed that Nb atoms form distorted NbO6 octahedra, which are isolated at low Nb2O5 content, whereas at higher Nb2O5 content they form clusters. 11B NMR spectra of the glasses revealed the interaction between Nb2O5 and BO4 tetrahedral units, which results in a partial transformation of tetrahedral BO4 units to trigonal BO3 units and the formation of mixed B(OP)4− n (ONb) n units. [Copyright &y& Elsevier]

Glasses of the ternary system ZnO–Bi2O3–P2O5 were prepared and studied in two compositional series 50ZnO– xBi2O3–(50 − x)P2O5 and (50 − y)ZnO– yBi2O3–50P2O5. Two distinct glass-forming regions were found in the 50ZnO– xBi2O3–(50 − x)P2O5 glass series with x = 0–10 and 20–35 mol.% Bi2O3. All prepared Bi2O3-containing glasses reveal a high chemical durability. Small additions of Bi2O3 (∼5 mol.%) improve thermal stability of glasses. All glasses crystallize on heating within the temperature range of 505–583 °C. Structural studies by Raman and 31P MAS NMR spectroscopies showed the rapid depolymerisation of phosphate chains within the first region with x = 0–15 and the presence of isolated Q0 phosphate units within the second region with x = 20–35. Raman studies showed that bismuth is incorporated in the glass structure in BiO6 units and their vibrational bands were observed within the spectral region of 350–700 cm−1. The evolution of properties and the spectroscopic data are both in accordance with a network former effect of Bi2O3. [ABSTRACT FROM AUTHOR]

Abstract: The structure of 50ZnO–10B2O3–40P2O5+xTiO2 glasses prepared by slow cooling (for x=0–24mol% TiO2) or by quenching (for x=28–64mol% TiO2) was studied by Raman, 31P and 11B MAS NMR spectroscopy. TiO2 incorporates into the glass structure, which results in a decrease in the molar volume and an increase in the glass transition temperature. According to Raman spectra Ti atoms form distorted TiO6 octahedra and their incorporation into the structural network results in the depolymerization of phosphate chains. 11B NMR spectra of the glasses with increasing TiO2 content show gradual changes from one symmetrical signal of B(OP)4 units to a broad complex signal which was separated into five signals ascribed to four different types of BO4 units and one BO3 unit. With increasing TiO2 content a part of boron atoms changes from tetrahedral BO4 to trigonal BO3 units, which is ascribed to the formation of TiO6 units in the glass structure. [Copyright &y& Elsevier]

In present study glasses of the system Ag 2 O-GeO 2 -P 2 O 5 were studied in the compositional series (50−x)Ag 2 O-xGeO 2 -50P 2 O 5 with x = 0−40 mol%. Ag 2 O substitution by GeO 2 results in a significant increase of both glass transition temperature, T g , and crystallization temperature, T c , up to 628 °C (T g) and 851 °C (T c) at x = 40 mol% GeO 2. The glass structure was investigated from the analysis of 31P MAS NMR and Raman spectra. Both methods show transformation of phosphate glass network formed mainly by Q2 units to germanate-phosphate network formed by Q1 xGe and Q2 1Ge phosphate units and germanate units. Raman spectra, in addition, reveal evolution of P‒O‒P linkages to P‒O‒Ge and Ge‒O‒Ge linkages through the glass series. DC conductivity trend upon GeO 2 addition showed non-monotonic behaviour, which is related to structural changes in the glass-network. • Silver phosphate glasses with a high germanium dioxide content were prepared and studied. • An increase in thermal and chemical stability of glasses by GeO 2 additions was observed. • Structure of glasses was studied by Raman and 31P MAS NMR spectroscopy. • Decreasing Ag 2 O content is associated with higher interconnection of glass network. [ABSTRACT FROM AUTHOR]

• Glass-forming region in the system BaO-WO 3 -P 2 O 5 was determined. • High ionicity limits glass formation in BaO rich glasses. • Glass structure and properties were studied in five compositional series. • Possible coordination change of tungsten from WO 6 to WO 4 revealed by Raman spectra. • Clustering of tungstate octahedra depends on the BaO/P 2 O 5 ratio. The purpose of this work was to prepare and study new glasses from the system BaO-WO 3 –P 2 O 5 focusing on their basic physical properties and studying their structure by Raman and 31P NMR spectroscopies in five compositional glass series. The glass transition temperature increases in all compositional series with increasing WO 3 content. The 31P MAS NMR spectra of the glasses revealed depolymerization of the phosphate network. In the Raman spectra of glasses with a low WO 3 content, two strong vibrational bands at 885 and 945 cm−1 were assigned to the vibration of W O and W-O− bonds in tungstate structural units. In glasses with a high WO 3 content, a broad band at 820–841 cm−1, ascribed to W-O-W bonds, indicated the formation of clusters composed of WO 6 units. Raman spectra also revealed partial transformation of WO 6 units into WO 4 units in glasses with a low P 2 O 5 content. [ABSTRACT FROM AUTHOR]

Na-V-P-Nb-based materials have gained substantial recognition as cathode materials in high-rate sodium-ion batteries due to their unique properties and compositions, comprising both alkali and transition metal ions, which allow them to exhibit a mixed ionic–polaronic conduction mechanism. In this study, the impact of introducing two transition metal oxides, V2O5 and Nb2O5, on the thermal, (micro)structural, and electrical properties of the 35Na2O-25V2O5-(40 − x)P2O5 − xNb2O5 system is examined. The starting glass shows the highest values of DC conductivity, σDC, reaching 1.45 × 10−8 Ω−1 cm−1 at 303 K, along with a glass transition temperature, Tg, of 371 °C. The incorporation of Nb2O5 influences both σDC and Tg, resulting in non-linear trends, with the lowest values observed for the glass with x = 20 mol%. Electron paramagnetic resonance measurements and vibrational spectroscopy results suggest that the observed non-monotonic trend in σDC arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V4+ ions and the introduction of Nb2O5, which disrupts the predominantly mixed vanadate–phosphate network within the starting glasses, consequently impeding polaronic transport. The mechanism of electrical transport is investigated using the model-free Summerfield scaling procedure, revealing the presence of mixed ionic–polaronic conductivity in glasses where x < 10 mol%, whereas for x ≥ 10 mol%, the ionic conductivity mechanism becomes prominent. To assess the impact of the V2O5 content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V2O5 content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution. [ABSTRACT FROM AUTHOR]

Sodium-phosphate-based glass-ceramics (GCs) are promising materials for a wide range of applications, including solid-state sodium-ion batteries, microelectronic packaging substrates, and humidity sensors. This study investigated the impact of 24 h heat-treatments (HT) at varying temperatures on Na-Ge-P glass, with a focus on (micro)structural, electrical, and dielectric properties of prepared GCs. Various techniques such as powder X-ray diffraction (PXRD), infrared spectroscopy-attenuated total reflection (IR-ATR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) were employed. With the elevation of HT temperature, crystallinity progressively rose; at 450 °C, the microstructure retained amorphous traits featuring nanometric grains, whereas at 550 °C, HT resulted in fully crystallized structures characterized by square-shaped micron-scale grains of NaPO3. The insight into the evaluation of electrical and dielectric properties was provided by Solid-State Impedance Spectroscopy (SS-IS), revealing a strong correlation with the conditions of controlled crystallization and observed (micro)structure. Compared to the initial glass, which showed DC conductivity (σDC) on the order of magnitude 10−7 Ω−1 cm−1 at 393 K, the obtained GCs exhibited a lower σDC ranging from 10−8 to 10−10 Ω−1 cm−1. With the rise in HT temperature, σDC further decreased due to the crystallization of the NaPO3 phase, depleting the glass matrix of mobile Na+ ions. The prepared GCs showed improved dielectric parameters in comparison to the initial glass, with a noticeable increase in dielectric constant values (~20) followed by a decline in dielectric loss (~10−3) values as the HT temperatures rise. Particularly, the GC obtained at @450 stood out as the optimal sample, showcasing an elevated dielectric constant and low dielectric loss value, along with moderate ionic conductivity. This research uncovers the intricate relationship between heat-treatment conditions and material properties, emphasizing that controlled crystallization allows for precise modifications to microstructure and phase composition within the remaining glassy phase, ultimately facilitating the fine-tuning of material properties. [ABSTRACT FROM AUTHOR]

Abstract This work presents a study on the structure, thermal behavior and properties of (100-x)[0.5Li 2 O-0.1B 2 O 3 -0.4P 2 O 5 ]-xTeO 2 glasses prepared within the concentration range of x = 0–80 mol% TeO 2. The structure of the glasses was studied with a combined Raman, 31P and 11B MAS NMR spectroscopy. 31P MAS NMR and Raman spectrum of the pure 50Li 2 O-10B 2 O 3 -40P 2 O 5 glass indicates the co-existence of Q2 and Q1 phosphate units in the glass structure. Raman spectra of TeO 2 containing glasses revealed that TeO 2 is incorporated in the structural network in the form of TeO 3 and TeO 4 (TeO 3+1) units. The ratio of TeO 4 /TeO 3 increases with rising TeO 2 content. Apart from the formation of P‒O‒Te and Te‒O‒Te bonds, the formation of B‒O‒Te bonds in the form of mixed tetrahedral units B(OP) 4-n (OTe) n also takes place as shown by 11B MAS NMR spectroscopy. The structural studies were correlated with the thermal behavior and physical properties of glasses (density, molar volume, chemical durability and refractive index). DSC studies showed that all glasses crystallize on heating within a temperature region of 400–550 °C and the surface nucleation mechanism prevails over the internal one. The crystallization temperature decreases with increasing TeO 2 content. The compounds formed by crystallization were LiPO 3 , Li 4 P 2 O 7 , BPO 4 and α-TeO 2. Glass transition temperature and dilatometric softening temperature, estimated from thermodilatometry curves, decrease with increasing TeO 2 content, whereas the thermal expansion coefficient increases. Graphical abstract The compositional dependences of glass transition temperature, T g , dilatometric softening temperature, T d , and thermal expansion coefficient, α , of the (100-x)[0.5Li 2 O-0.1B 2 O 3 -0.4P 2 O 5 ]-xTeO 2 glasses, obtained from dilatometric curves. fx1 Highlights • Structure of Li 2 O-B 2 O 3 -P 2 O 5 -TeO 2 glasses. • Raman, 31P and 11B spectroscopy. • Thermal behavior and physical properties of Li 2 O-B 2 O 3 -P 2 O 5 -TeO 2 glasses. • Relationships between structure, thermal behavior and physical properties. [ABSTRACT FROM AUTHOR]

Differential scanning calorimetry (DSC), dilatometry and X-ray diffraction have been used to study thermal behavior and stability of glasses prepared simultaneously in Al2O3 or Pt crucibles in compositional series (40 − x)MgO-xFe2O3-60P2O5 within the concentration range of x = 0-40 mol% Fe2O3. Mössbauer spectra showed that all glasses with Fe2O3 contained both Fe(II) and Fe(III) ions. The contamination glasses from alumina crucibles ranged from 0.3 to 0.9 mol% Al2O3. The replacement of MgO by Fe2O3 resulted in a gradual decrease in glass transition temperature and dilatometric softening temperature, whereas thermal expansion coefficient did not change significantly. The DSC curves showed that all glasses crystallize on heating in the broad temperature range ≈ 560-900 °C. Crystallization temperature decreases with increasing Fe2O3 content. The highest tendency toward crystallization was found for the glass containing 40 mol% Fe2O3. X-ray diffraction measurements showed that the major compounds formed by glass crystallization were Mg(PO3)2, Fe(PO3)3, Fe3(P2O7)2 and FePO4. All thermoanalytical studies showed differences in thermal behavior of glasses prepared in Al2O3 or Pt crucibles. [ABSTRACT FROM AUTHOR]

The present investigation deals with the study of the structure, properties and thermal behaviour of Na 2 O–P 2 O 5 –Nb 2 O 5 glasses prepared in the compositional series 40 Na 2 O- (60-x) P 2 O 5 - x Nb 2 O 5 (x=0–40 ​mol% Nb 2 O 5). The modification of starting 40 Na 2 O– 60 P 2 O 5 glass by Nb 2 O 5 revealed changes both in the structure and properties. The glass density steeply increases with increasing Nb 2 O 5 content while the molar volume decreases. Parent sodium ultraphosphate glass was covered with a thin layer of partially hydrolysed glass in air. The chemical durability of Nb 2 O 5 containing glasses was high. The replacement of P 2 O 5 by Nb 2 O 5 resulted in a gradual increase in the refraction index as well as in an increase in glass transition temperature and dilatometric softening temperature. DSC measurements demonstrated that glasses crystallize under heating in the temperature range of 330–880°C. The lowest thermal stability was found for the glass containing 40 ​mol% Nb 2 O 5. The Raman and NMR spectra indicated that the structure of 40Na 2 O–60P 2 O 5 glass is formed mainly by Q2 and Q1 phosphate units interconnected by P–O–P bonds. The replacement of P 2 O 5 by Nb 2 O 5 leads to depolymerization and the partial transformation of Q2 units into Q1 units and finally to isolated Q0 units. Nb 2 O 5 forms in the glass structure NbO 6 octahedra. [Display omitted] • Structure of Na 2 O–P 2 O 5 –Nb 2 O 5. • Raman and 31P MAS spectroscopy. • Thermal behavior and physical properties of Na 2 O–P 2 O 5 –Nb 2 O 5 glasses. • Structure, thermal behavior and physical properties relationships. [ABSTRACT FROM AUTHOR]

Abstract: Lithium borophosphate glasses with addition of germanium oxide were studied along the compositional series (100− x)[0.5Li2O–0.1B2O3–0.4P2O5]–xGeO2, with x =0–25mol.%. Their properties (density, glass transition temperature, coefficient of thermal expansion, chemical durability) were measured and their structure was studied by 31P and 11B MAS NMR spectroscopy and Raman spectroscopy. The addition of GeO2 to the parent borophosphate glass results in an increase of their glass transition temperature, while their chemical durability only slightly decreases. 31P MAS NMR and Raman spectra reflect the depolymerization of phosphate chains by the incorporation of GeO n polyhedra. 11B MAS NMR spectra reveal the formation of mixed structural units B(OP)3(OGe) in the borophosphate glasses and the decomposition of 11B MAS NMR spectra brings quantitative data on the number of BO3 and B(OP)3(OGe) structural units. A small amount of BO3 trigonal units is formed in the glasses as well. [Copyright &y& Elsevier]

• Glasses-(ceramics) from Na 2 O-V 2 O 5 -(Al 2 O 3)-P 2 O 5 Nb 2 O 5 system are explored as catalysts. • Samples with ≥55 mol% V 2 O 5 exhibit the highest activity and selectivity toward epoxide, in cyclooctene epoxidation. • Tested oxidants, tert ‑butyl hydroperoxide in water and in decane provided good catalytic performance. • The starting material can be recovered and reused in the 2nd run. • The best catalytic performance is followed by high electrical conductivity. Glass-(ceramic) samples were prepared by melting mixtures of Na 2 O-V 2 O 5 -(Al 2 O 3)-P 2 O 5 -Nb 2 O 5 in various molar ratios, and their catalytic performances were correlated to the structural, thermal, and electrical properties. The catalysts were tested in an epoxidation reaction, with tert ‑butyl hydroperoxide in decane and water as oxidants. Samples containing the highest vanadium content are highlighted as the best catalysts (cyclooctene conversion 70–90 %), highly selective towards the desired epoxide (70–80 %). At the same time, high electrical conductivity is observed with the value of ∼10–5 S cm–1 @30 °C, which is 4–6 orders of magnitude higher in comparison to other studied samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Differential thermal analysis and thermodilatometry have been used to study the thermal behaviour of glasses in the ZnO–P2O5–TeO2 system prepared in compositional series (100− x)[0.5ZnO–0.5P2O5]–xTeO2 (X-series) and 50ZnO–(50− y)P2O5–yTeO2 (Y-series) within the concentration range of x =0–60 and y =0–40mol% TeO2. The addition of TeO2 to the starting zinc metaphosphate glass resulted in a gradual increase of thermal expansion coefficient from 12.2 up to 16.6ppm°C−1, whereas glass transition temperature and dilatometric softening temperature reveal a minimum at the glass with x =30mol% and y =10mol% TeO2. All glasses crystallize on heating within the temperature range ∼500–700°C. The contribution of the surface crystallization mechanism over the internal one increases with increasing TeO2 content. Major compounds formed by crystallization were Zn(PO3)2 and Zn2P2O7. [Copyright &y& Elsevier]

Abstract: Glasses in the ternary ZnO–P2O5–TeO2 system were prepared and studied in two compositional series (100−x)[0.5ZnO–0.5P2O5]–xTeO2 (X-series) and 50ZnO–(50−y)P2O5–yTeO2 (Y-series) within the concentration range of x=0–60 and y=0–40mol% TeO2. Their structure was studied by Raman and 31P MAS NMR spectroscopies. The incorporation of TeOx units into the structural network is associated with the depolymerisation of phosphate chain structure as revealed by both methods. At a high TeO2 content isolated PO4 tetrahedra are formed in the structure of glass series Y, while diphosphate O3P–O–PO3 groups are present in the structure of the glass series X. In the structure of glass series Y tellurium atoms form predominantly TeO3 trigonal pyramids, whereas in the X glass series TeO4 trigonal bipyramids prevail in the glass structure. The addition of TeO2 to the parent zinc metaphosphate glass results in a decrease of glass transition temperature in both compositional series associated with the replacement of stronger P―O bonds by weaker Te―O bonds. [Copyright &y& Elsevier]

Abstract: Zinc borophosphate glasses doped with TeO2 were studied in the compositional series (100− x)[0.5ZnO–0.1B2O3–0.4P2O5]–xTeO2 in a broad concentration range of x =0–80mol% TeO2. The structure of the glasses was studied by Raman and IR spectroscopy and by 31P and 11B MAS NMR spectroscopy. According to the Raman and IR spectra, TeO2 is incorporated in the structural network in the form of TeO3, TeO3+1 and TeO4 structural units. The ratio of TeO4/TeO3 increases with increasing TeO2 content in the glasses. The incorporation of TeO x units into the glass network is associated with the depolymerisation of phosphate chains, as revealed by Raman spectroscopy. The incorporation of TeO2 modifies also the coordination of boron atoms, where B(OP)4 structural units are gradually replaced by B(OP)4−n (OTe) n units. The addition of TeO2 to the parent zinc borophosphate glass results in a decrease of glass transition temperature associated with the replacement of stronger P–O and B–O bonds by weaker Te–O bonds. Chemical durability of glasses reveals a minimum at the glass containing 10mol% TeO2, but with further additions of TeO2 it improves and the glasses with a high TeO2 content reveal better durability than the parent zinc borophosphate glass. [Copyright &y& Elsevier]

Abstract: Local and medium range order in the glass system 50Ag2O–50[(B2O3)x–(P2O5)1-x] (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) have been investigated by high-resolution solid state nuclear magnetic resonance (NMR) techniques. The detailed local site distribution has been derived from deconvolution analysis of the 11B and 31P magic-angle spinning (MAS) NMR signals. Quantitative information regarding the extent of boron–oxygen–phosphorus connectivity has been obtained on the basis of 11B[31P} and 31P{11B} rotational echo double resonance experiments. Incorporation of borate into silver metaphosphate glasses produces four-coordinate BO4/2- sites, which crosslink the metaphosphate chains, resulting in a significant increase in the glass transition temperature. Furthermore, the presence of borate favors the disproportionation of P(2) chain-like units into P(1) and P(3) sites, an effect not observed in binary alkali phosphate glasses. Finally, borate incorporation beyond x=0.3 results in the formation of neutral BO3/2 units, indicating some net charge transfer from the borate to the phosphate network former species. This latter result corresponds to the general metal ion scavenging effect observed for phosphate species in other mixed network former glass systems. In the present system, the effect is relatively moderate, however, suggesting that anionic BO4/2- groups are stabilized by the interaction with the phosphate groups. [Copyright &y& Elsevier]

This study investigates the influence of structural modifications induced by the introduction of Nb 2 O 5 on the thermal, (micro)structural, and electrical properties of quaternary system 35Na 2 O–10V 2 O 5 -(55– x)P 2 O 5 - x Nb 2 O 5 (x = 0–40 mol%). Non-monotonic trends in DC conductivity and activation energy are attributed to the facilitating effect of Nb 2 O 5 on the transport of Na + ions, confirming the mixed glass former effect. The results demonstrate that the electrical conductivity mechanism is purely ionic, with V 2 O 5 acting as both, glass modifier and network-former with vanadate units being in predominantly 4-fold coordination and without actively participating in the conduction process. Complementary Raman and IR-ATR spectroscopic studies in combination with solid-state impedance spectroscopy (SS-IS) reveal a strong correlation between structural and electrical properties indicating that the enhancement in conductivity is driven by the formation of mixed niobate-phosphate glass network. The increase in conductivity is followed by a gradual transition of glass structure from a predominantly phosphate glass network (x ≤ 10, Region I) into a mixed niobate-phosphate glass network (10 ≤ x ≤ 20, Region II). The conductivity increases by a factor of ∼4.5 within the series reaching the highest value of 3.29 × 10−10 Ω−1 cm−1 for Nb-20 glass. In the predominantly niobate network (x ≥ 25, Region III), the 3D clustering of NbO 6 octahedra hinders the transport of Na + ions. The scaling features of the conductivity spectra additionally confirm the ionic mechanism of electrical transport and provide insight into the local dynamics of Na+ ions. [Display omitted] [ABSTRACT FROM AUTHOR]

The scaling behaviour of six series of mixed ion-polaron glasses with the composition x WO 3 /MoO 3 -(30–0.5 x)Li 2 O/Na 2 O/Ag 2 O-(30–0.5 x)ZnO-40P 2 O 5 , 0 ≤ x ≤ 60 mol%, has been studied using Summerfield and Sidebottom scaling procedures that are model free. The validity of the Sidebottom scaling procedure for each individual glass confirms that all glasses obey time-temperature superposition principle implying that the conduction mechanism does not change with temperature. On the other hand, Summerfield scaling is not found valid for all glasses. First, this deviation is observed in all glasses containing Li 2 O up to 20 mol% of MoO 3 /WO 3. We relate this result to a non-typical interaction of Li+ ion with the compact zinc phosphate network resulting either in change of its hopping distance or in available conduction pathways for it as a function of temperature. Second, non-Summerfield scaling was also observed for glasses containing Li 2 O/Na 2 O/Ag 2 O with about 30 to 40 mol% of WO 3. Thus, the origin of this deviation lies in the significant amounts of both types of charge carriers - ions and polarons, and their differently thermally activated mobilities. Unusual Li+ dynamics and mixed ionic-polaronic conduction in zinc phosphate glasses detected by scaling conductivity spectra. Image 1 [ABSTRACT FROM AUTHOR]

This study reports on the nature of electrical transport and role of structural changes induced by different type and content of TMO in Ag–containing glasses of x TMO–(30–0.5 x )Ag 2 O–(30–0.5 x )ZnO–40P 2 O 5 (TMO = MoO 3 /WO 3 , 0 ≤  x  ≤ 60 mol%) composition. Raman spectra show clustering of WO 6 units in glasses with high WO 3 content while the addition of MoO 3 induces a gradual change of MoO 6 octahedra to MoO 4 tetrahedra both being cross-linked with phosphate units without clustering. For WO 3 glasses, minimum in DC conductivity is observed at 30–40 mol% of WO 3 for temperatures from 303 to 513 K, followed by an increase in conductivity with further WO 3 addition due to an increase in polaronic contribution. Observed turnover suggests a distinct transition from predominantly ionic to predominantly polaronic transport. On the contrary, for MoO 3 glasses, conductivity decreases in the whole mixed compositional range indicating that the nature of transport is dominated by ionic component throughout the measured temperature range. A comparative study of Ag + , Li + , Na + transport in MoO 3 /WO 3 glasses reveals a strong correlation between pre-exponential factor and activation energy, which allows detection of the prevalence of conduction mechanism. Finally, the results demonstrate that Ag 2 O–WO 3 –ZnO–P 2 O 5 glass system is a promising electrically tunable material with significant contributions of ionic or polaronic conductivity depending on composition. [ABSTRACT FROM AUTHOR]

Transformation of electrical transport from ionic to polaronic in glasses, which are a potential class of new cathode materials, has been investigated in four series containing WO3/MoO3 and Li+/Na+ ions, namely: xWO3-(30−0.5 x)Li2O-(30−0.5 x)ZnO-40P2O5, xWO3-(30−0.5 x)Na2O-(30.5 x)ZnO-40P2O5, xMoO3-(30−0.5 x)Li2O-(30−0.5 x)ZnO-40P2O5, and xMoO3-(30−0.5 x)Na2O-(30−0.5 x)ZnO-40P2O5, 0 ≤ x ≤ 60, (mol%). This study reports a detailed analysis of the role of structural modifications and its implications on the origin of electrical transport in these mixed ionic-polaron glasses. Raman spectra show the clustering of WO6 units by the formation of W-O-W bonds in glasses with high WO3 content while the coexistence of MoO4 and MoO6 units is evidenced in glasses containing MoO3 with no clustering of MoO6 octahedra. Consequently, DC conductivity of tungstate glasses with either Li+ or Na+ exhibits a transition from ionic to polaronic showing a minimum at about 20-30 mol% of WO3 as a result of ion-polaron interactions followed by a sharp increase for six orders of magnitude as WO3 content increases. The formation of WO6 clusters involved in W-O-W linkages for tungsten glasses plays a key role in significant increase in DC conductivity. On the other hand, DC conductivity is almost constant for glasses containing MoO3 suggesting an independent ionic and polaronic transport pathways for glasses containing 10-50 mol% of MoO3. [ABSTRACT FROM AUTHOR]

Electrical transport in mixed ion-polaron glasses has been investigated in four series of glasses containing transition metal oxides (TMO) namely WO3/MoO3, and Na+/Ag+ ions with the composition xWO3-(30-0.5x)Na2O-(30-0.5x)ZnO-40P2O5, xWO3-(30-0.5x)Ag2O-(30-0.5x)ZnO-40P2O5, xMoO3-(30-0.5x)Na2O-(30-0.5x)ZnO-40P2O5, and xMoO3-(30-0.5x)Ag2O-(30-0.5x)ZnO-40P2O5, 0 ≤ x ≤ 60 (mol%). The DC conductivity of Na-glasses up to 30 mol% of WO3 and MoO3 is almost identical due to the dominance of ionic conductivity. In this compositional region, the introduction of tungstate and molybdate units increases the mobility of sodium ions and compensates the decrease in sodium number density. On the other hand, with increasing WO3 and MoO3 content and decreasing Ag+ ion concentration in Ag-glasses the DC conductivity decreases for few orders of magnitude. A significant difference in conductivity is observed for glasses with higher WO3 and MoO3 content. While for glasses containing WO3 the conductivity rapidly increases due to a huge polaronic contribution indicating a turnover from predominantly ionic to polaronic transport, the conductivity for MoO3-glasses decreases in the entire mixed compositional range suggesting dominant ionic transport. The changes in the conduction mechanism with the systematic alternation of the glass composition have been analyzed in correlation with the structural modifications and variations of molybdenum and tungsten in different oxidation states. [ABSTRACT FROM AUTHOR]

Effect of the structural changes, electrical conductivity, and dielectric properties on the addition of a third glass-former, GeO2, to the borophosphate glasses, 40Li2O-10B2O3-(50 - x)P2O5-xGeO2, x = 0-25 mol %, has been studied. Introduction of GeO2 causes the structural modifications in the glass network, which results in a continuous increase in electrical conductivity. Glasses with low GeO2 content, up to 10 mol %, show a rapid increase in dc conductivity as a result of the interlinkage of slightly depolymerized phosphate chains and negatively charged [GeO4]- units, which enhances the migration of Li+ ions. The Li+ ions compensate these delocalized charges connecting both phosphate and germanium units, which results in reduction of both bond effectiveness and binding energy of Li+ ions and therefore enables their hop to the next charge-compensating site. For higher GeO2 content, the dc conductivity increases slightly, tending to approach a maximum in Li+ ion mobility caused by the incorporation of GeO2 units into phosphate network combined with conversion of GeO4 to GeO6 units. The strong cross-linkage of germanium and phosphate units creates heteroatomic P-O-Ge bonds responsible for more effectively trapped Li+ ions. A close correspondence between dielectric and conductivity parameters at high frequencies indicates that the increase in conductivity indeed is controlled by the modification of structure as a function of GeO2 addition. [ABSTRACT FROM AUTHOR]

Theeffect of adding TeO2into (100 – x)[0.5Ag2O – 0.1B2O3–0.4P2O5] – xTeO2,with 0–80 mol % TeO2glass, on the structuralchanges and electrical properties has been investigated. DSC and thermodilatomerywere used to study their thermal behavior, structure was studied byRaman spectroscopy, and electrical properties have been studied byimpedance spectroscopy over a wide temperature and frequency range.The introduction of TeO2as a third glass former to theglass network causes the structural transformation from TeO3(tp) to TeO4(tbp) which contributes to the changes inconductivity. The glasses with low TeO2content show onlya slow decrease in dc conductivity with addition of TeO2due to the increase of the number of nonbridging oxygens, whichincreases the mobility of Ag+ions. The steep decreasein conductivity for glasses containing more than 40 mol % TeO2is a result of decrease of the Ag2O content andstronger cross-linkage in glass network through the formation of moreTe–eqOax–Te bonds in TeO4tbp units. The glasses obey ac conductivity scaling with respectto temperature, implying that the dynamic process is not temperaturedependent. On the other hand, the scaling of the spectra for differentglass compositions showed the deviations from the Summerfield scalingbecause of the local structural disorder which occurs as a resultof the structural modifications in the tellurite glass network. [ABSTRACT FROM AUTHOR]

Phosphate glasses containing transition metal oxides such as MoO 3 and WO 3 are well-known for their semiconducting nature with polaronic conduction mechanism. These glasses can also accommodate a relatively high amount of alkali and silver oxides which give rise to ionic conductivity. Such a large compositional and preparation variability enables tuning of the types and mechanisms of the electrical conduction and makes these materials attractive for application in modern electrochemical devices. In this contribution, we discuss various factors that influence electrical transport in these glasses, from simple binary WO 3 /MoO 3 -P 2 O 5 systems to complex ones containing variable amounts of alkali/silver oxides. Interestingly, WO 3 and MoO 3 can have very different roles in the electrical conduction in these materials. While MoO 3 contributes weakly via polaronic transport in phosphate glasses, it strongly increases the mobility of alkali/silver ions by forming the mixed phosphate-molybdate network. On the other hand, the role of WO 3 depends on the glass composition; it can contribute either directly, by introducing significant polaronic conductivity, or indirectly, by facilitating the transport of alkali/silver ions. The former behaviour is related to the formation of clusters of tungsten units in the glass network which enable fast transport of polarons whereas the latter one originates from the facilitating effect of mixed phosphate-tungstate units on the dynamics of alkali ions. • WO 3 and MoO 3 can exhibit different influence on structural and transport properties of phosphate glasses. • Clustering of tungsten units in glass network facilitates polaronic conductivity. • Formation of mixed phosphate-molybdate and phosphate-tungstate units increases mobility of alkali ions. [ABSTRACT FROM AUTHOR]

A series of glass-ceramics were prepared by heat-treatments of 40Na2O-30MoO3-30P2O5 (in mol%) glass in a temperature range from 380 (Tg) to 490 °C (Tc) and for 1–24 h. The prepared glass-ceramics contain from 2 to 25 wt.% of crystalline NaMoO2PO4. The sodium-ion conductivity in these materials decreases up to one order of magnitude with an increase in the degree of crystallization due to the immobilization of sodium ions in crystalline NaMoO2PO4. The transport of sodium ions in these materials occurs primarily through the dominant continuous glassy phase, and it is weakly affected by the sporadically distributed crystalline grains. However, the prepared glass-ceramics exhibit high proton conductivity in a humid atmosphere and remarkable humidity-sensing properties; this could be related to crystalline NaMoO2PO4, which provides sites for water adsorption. The glass-ceramic prepared at 450 °C for 24 h shows the best humidity-sensing performance among all samples, showing an increase in proton conductivity for more than seven orders of magnitude with the increase in relative humidity from 0% to 95%. Under a highly humid atmosphere (95% relative humidity and 25 °C), the proton conductivity of this glass-ceramic reaches 5.2 × 10−3 (Ω cm)−1. Moreover, the electrical response of these materials on the change in the relative humidity is linear and reversible in the entire range of the relative humidity, which indicates that they are novel promising candidates for application as humidity sensors. [ABSTRACT FROM AUTHOR]

The structural relaxation of three compositional series of PbO–WO 3–P 2O 5 glasses with composition (0.5 −  x/2)PbO· xWO 3·(0.5 −  x/2)P 2O 5, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; 0.5PbO· xWO 3·(0.5 −  x)P 2O 5, x = 0, 0.1, 0.2, and 0.3; and (0.5 −  x)PbO· xWO 3·0.5P 2O 5, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was studied by thermomechanical analysis. The structural relaxation was studied in the transformation region using the Tool–Narayanaswamy–Moynihan’s and Tool–Narayanaswamy–Mazurin’s models. The relaxation function of Kohlrausch Williams and Watts was used. The parameters of both models were calculated by nonlinear regression analysis of thermodilatometric curves measured by thermomechanical analyzer under the constant load. Both models very well describe the experimental data. It was found that the modulus is increasing with increasing amount of WO 3 in all glasses. On the contrary, the width of the spectrum of relaxation times is decreasing with increasing amount of WO 3 in all studied glasses. Both models possess the values of metastable melt thermal expansion coefficient equal to their experimental value. [ABSTRACT FROM AUTHOR]

Abstract: Lithium ion transport upon the addition of germanium oxide in a series of mixed glass former lithium borophosphate glasses has been investigated. The electrical and dielectric properties of (100 − x)[0.5Li2O–0.1B2O3–0.4P2O5]–xGeO2 with 0–25 mol% GeO2 glasses have been studied over a wide temperature (183–523 K) and frequency range (0.01 Hz–1 MHz). The increase in dc conductivity with the addition of GeO2 is attributed to the formation of ion conducting channels arising from the structural modification and formation of the P–O–Ge linkages, resulting in an easy migration of Li+ ions along these bonds. At higher GeO2 content glass network becomes more densely packed and ionic conductivity is slightly hindered as a consequence of the increase of bonding forces inside the network. Such a decrease in the conductivity is more reflection of the stronger cross-linkage in the glass network than that of the slight decrease in the Li+ ion concentration. The electrical modulus formalism is used to describe the dielectric relaxation. The scaling of the ac conductivity results in an excellent collapse onto common master curve whereas the electrical modulus spectra showed slight deviation indicating the distribution of relaxation times caused by the presence of various structural units in the glass network. [Copyright &y& Elsevier]