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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]

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]

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 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]

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]

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]

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]

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]

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]