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This work provides new insights into the nature of the polaronic transport in xV2O5–(100−x)P2O5, 41 ≤ x ≤ 89 mol% glasses from analysis of their conductivity over a wide range of frequencies and temperatures, and correlation of the electrical parameters to the structural models of these materials. The results show that the linear increase in direct current (DC) conductivity with the increase in V2O5 could be related to the formation of a vanadate subnetwork, which is characterized by a length distribution of V–O bonds and variations in linkages between different vanadate units. Such a structurally complex network offers multiple conduction pathways which are favorable for polaron hopping. The Summerfield scaling of conductivity spectra reveals a temperature‐invariant mechanism of polaron transport for all glasses and the same local structural environment of polarons at higher V2O5 contents due to the same ratio of vanadate units present in the network. Also, this study highlights the similarities and differences in the nature of the polaronic transport of vanadate–phosphate glasses and other polaronically conducting phosphate glasses containing WO3, MoO3, and Fe2O3, and pins down a pivotal role of the glass structure in electrical processes in these materials. [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]

Bulk glasses of the series (100−x)[0.4Na2O-0.2Nb2O5-0.4P2O5]-xB2O3 with x = 0–48 mol% B2O3 were prepared by slow cooling in air. Their glass transition temperature increases within the range of 0–16 mol% B2O3, but further additions of B2O3 result in its decrease. Their structure was investigated by Raman, 11B, and 31P MAS NMR spectroscopy. The relative number of BO4 units decreases with increasing B2O3 content, while the number of BO3 units increases up to 59 % at x = 48. The upfield shift of a broad resonance peak in the 31P MAS NMR spectra is ascribed to an increasing connectedness of the structural network with increasing B2O3 content. Strong Raman band at 916–929 cm−1 shows on the presence of NbO6 octahedra in the structural network of these glasses. With the B2O3 addition, a decrease in DC conductivity is observed, which is attributed to the decrease in the concentration of Na+ ions. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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: 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]

• 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]

• 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]

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]

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]

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: 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]

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 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]