Glass formation, properties and structure of glasses in the P2O5---WO3---K2O---Al2O3 system

Glass formation in the P₂O₅---WO₃---K₂O---Al₂O₃ system was investigated and the glass-forming regions are presented.

the properties of the glasses in the P₂O₅---WO₃---K₂O---Al₂O₃ system (Al₂O₃ 8 mol.%) are reported.

The colouration of glass was studied. It was found that W⁵⁺ ions make glass blue.

Infrared spectra were measured by means of making KBr pills. Results of the investigation suggest that P---O---P, P---O---W, and W---O---W bonds form a continuous network in the phosphate glasses. So we suggest that tungsten trioxide is a glass former.     

Study of electrical properties of MoO3–Fe2O3–P2O5 and SrO–Fe2O3–P2O5 glasses by impedance spectroscopy. II

The electrical and dielectric properties for three series of MoO₃–Fe₂O₃–P₂O₅ and one series of SrO–Fe₂O₃–P₂O₅ glasses were measured by impedance spectroscopy in the frequency range from 0.01 Hz to 3 MHz and over the temperature range from 303 to 473 K. It was shown in Part I that the MoO₃ is incorporated into phosphate network and the structure/properties are strongly influenced by the overall O/P ratio. The Fe₂O₃ content and Fe(II)/Fe_tot ratio in these glasses have significant effects on the electrical conductivity and dielectric permittivity. With decreasing Fe₂O₃ content in MoO₃–Fe₂O₃–P₂O₅ glasses with O/P at 3.5 the dc conductivity, σ_dc(ω) decreases for two orders of magnitude, which indicates that the conductivity for these glasses depends on Fe₂O₃ and is independent of the MoO₃ content. Also, the dielectric properties such as ^′(ω), ^″(ω) and σ_ac(ω) and their variation with frequency and temperature indicates a decrease in relaxation intensity with increase in the concentration of MoO₃. On the other hand, the dc conductivity for MoO₃–Fe₂O₃–P₂O₅ glasses with O/P > 3.5 increases with the substitution of MoO₃ which has been explained by an increase in the number of non-bridging oxygens and formation of Fe–O–P bonds that are responsible for formation of small polarons. The increase in the dielectric permittivity, ^′(ω) with increasing MoO₃ content is attributed to the increase in the deformation of glass network with increasing bonding defects. For SrO–Fe₂O₃–P₂O₅ glasses the conductivity and dielectric permittivity remained constant with increasing SrO.     

Glass formation in the PbBr2–PbCl2–PbF2–PbO–P2O5 system

New glasses in the PbBr₂–PbCl₂–PbF₂–PbO–P₂O₅ system have been prepared and characterized. The glass-forming regions have been explored and the stability of the glasses against crystallization studied. Results show that the PbBr₂–PbCl₂–P₂O₅ ternary system has a broad glass-forming region which extends to 30 mol% P₂O₅. Most of the glasses in this system show strong stability against crystallization and some have glass transition temperatures as low as 146°C. When 5% PbO or 5% PbF₂ is introduced into the PbBr₂–PbCl₂–P₂O₅ system, the glass-forming region becomes smaller and the glass transition temperatures increase. However, the introduction of 2.5% PbF₂ and 2.5% PbO into the ternary system increases the glass transition temperature and broadens the glass-forming region. The introduction of PbF₂ alone improves the glass-forming ability of the system while the introduction of PbO alone lowers the glass-forming ability.     

Properties and structure of RO---Na2O---Al2O3---P2O5 (R = Mg, Ca, Sr, Ba) glasses

The properties and structure of (45 - x)RO · xNa₂O · 2.5Al₂O₃ · 52.5P₂O₅ (R = Mg, Ca, Sr, Ba, 0 x 31 mol%) glasses were investigated. The variation in the molar volumes of glasses in the MgO series is closely related to the formation of the end groups in the glasses with the substitution of Na⁺ ions for Mg²⁺ ions, resulting in a variation of the density and refractive index of the glasses. The properties of glasses containing CaO in terms of Na₂O substitution depend mainly on the low field strength of Na⁺ ions substituting for CaO even though the end groups occurring in the glasses increased. The variation in properties of the glasses containing SrO and BaO, some of which were substituted by Na₂O, could be explained by differences in masses, field strength and polarizability between the Na⁺ ions and the alkaline-earth ions due to a small variation in the structure of the glasses despite Na₂O substitution.     

Precipitation of In2O3 nano-crystallites from glasses in the system Na2O/B2O3/Al2O3/In2O3

Glasses in the system Na₂O/B₂O₃/Al₂O₃/In₂O₃ were melted and subsequently tempered in the range from 500 to 700 °C. Depending on the chemical composition, various crystalline phases were observed. From samples without Al₂O₃, In₂O₃ could not be crystallized from homogeneous glasses, because either spontaneous In₂O₃ crystallization occurred during cooling, or other phases such as NaInO₂ were formed during tempering. The addition of alumina, however, controlled the crystallization of In₂O₃. Depending on the crystallization temperature applied, the crystallite sizes were in the range from 13 to 53 nm. The glass matrix can be dissolved by soaking the powdered glass in water. This procedure can be used to prepare nano-crystalline In₂O₃-powders.     

Some characteristics of glass in the Al2O3---B2O3---SiO2 system from the gel

The colorless and transparent glasses in the Al₂O₃---B₂O₃---SiO₃ system with high B₂O₃ and SiO₂ content were prepared from gels at low temperature. Their IR spectra not only revealed the evolution of the gel to glass conversion, but also showed that the formation of mixed bonds in the glasses obtained did not show any effect due to the B₂O₃ content. The accuracy of the glass composition is dependent upon the SiO₂/B₂O₃ molar ratio. The higher the ratio, the less the deviation of the analyzed compositions of the resulting glasses from their original calculated values. It is obvious that the higher the ratio, the lower the thermal expansion coefficient and the higher the transformation temperature of the glass, and the temperature at which the thermal contraction reaches an equilibrium is higher.     

Toughened glass-ceramics containing ZrO2 and Al2O3 prepared by the sol-gel process from metal alkoxides

Glasses of compositions 5ZrO₂·5SiO₂(ZS), 5ZrO₂·Al₂O₃·4SiO₂(ZAS) and 5 5ZrO₂·0.5Al₂O₃·0.5Na₂O·4SiO₂(ZANS) were prepared by the sol-gel process from metal alkoxides and sintered to make glass-ceramics. Tetragonal ZrO₂ was precipitated by heat treatment at 900 to 1300°C. The activation energy for tetragonal ZrO₂ crystal growth was extremely high in Al₂O₃ containing glasses. ZAS and ZS were sintered to the near theoretical densities above 1200°C, at which the predominant phase was tetragonal ZrO₂. On the other hand, for ZANS, high densification was not attained owing to the large pores enclosed by the glass phase. Strength and fracture toughness increased with the densification and the crystal growth of tetragonal ZrO₂, reaching 450 MPa and 9 MN/m^1.5, respectively.     

Structure and Raman spectra of glasses containing several glass-forming oxides and no glass-modifying oxide

Binary glasses containing no modifying oxides, such as SiO₂---GeO₂, SiO₂---B₂O₃, SiO₂---P₂O₅, GeO₂---B₂O₃, Al₂O₃---P₂O₅ and ternary glasses SiO₂---GeO₂---P₂O₅, Al₂O₃---B₂O₃---P₂O₅, B₂O₃---SiO₂---P₂O₅, Al₂O₃---ZrO₂---P₂O₅ have been prepared by melting and CVD methods. The Raman spectra have also been measured. Structural characteristics of SiO₂, GeO₂, B₂O₃, P₂O₅ in different glass systems are analysed. There exist coordination number changes in B₂O₃- and GeO₂-containing glasses and linkage changes between tetrahedra (SiO₄) and (PO₄) in SiO₂ and P₂O₅ containing glasses. The structure of Al₂O₃ containing glasses is homogeneous and the structure of B₂O₃ containing glasses is inhomogeneous. These experimental results are in coincidence with the X-ray small angle scattering analysis.     

Nuclear magnetic resonance studies of alkaline earth phosphosilicate and aluminoborosilicate glasses

The ¹¹B, ²⁷Al, ²⁹Si and ³¹P magic angle spinning (MAS) NMR spectra of MO–P₂O₅, MO–SiO₂–P₂O₅ and MO(M^′₂O)–SiO₂–Al₂O₃–B₂O₃ (M=Mg, Ca, Sr and Ba, M^′=Na) glasses were examined. In binary MO–P₂O₅ (M=Ca and Mg) glasses, the distributions of the phosphate sites, P(Q_n), can be expressed by a theoretical prediction that P₂O₅ reacts quantitatively with MO. In the ternary 0.30MO–0.05SiO₂–0.65P₂O₅ glasses, the 6-coordinated silicon sites were detected, whose population increases in the order of MgOxCaO–0.05SiO₂–(0.95−x)P₂O₅ glasses, its population increases with an increase in f (=([P₂O₅]−[MO]−[B₂O₃]−[Na₂O])/[SiO₂]) and has maximum at f=9. The signal due to the 5-coordinated silicon atoms is also observed when x is smaller than 0.45. When three network-forming oxides such as SiO₂, Al₂O₃ and B₂O₃ coexist, Al₂O₃ reacts preferably with MO. The populations of 4-coordinated boron atoms, N₄, are expressed well with r/(1−r), where r=([Na₂O]−[Al₂O₃])/([Na₂O]−[Al₂O₃]+[B₂O₃]). The correlation of the Raman signal at 1210 and 1350 cm⁻¹ with the NMR signal of Si(Q₆) at −215 ppm is also seen.     

Effect of Al2O3 on phase separation and crystallization in ZnO---Al2O3---B2O3---SiO2 glasses

The effect of alumina on the phase separation and the crystallization of the glasses of composition (mol%) 18ZnO·30B₂O₃·52SiO₂ and O-40 Al₂O₃ was studied using an electron microscope and IR spectroscopy. The main crystalline phase appears in the microphase for which the compositions are not nearer to the crystal stoichiometry than the mean. The addition of Al₂O₃ suppresses the immiscibility but enhances the crystallizability.     

Characterisation of semiconducting V2O5–Bi2O3–TeO2 glasses through ultrasonic measurements

Tellurite containing vanadate (50−x)V₂O₅–xBi₂O₃–50TeO₂ glasses with different bismuth (x=0, 5, 10, 15, 20 and 25 wt%) contents have been prepared by rapid quenching method. Ultrasonic velocities (both longitudinal and shear) and attenuation (for longitudinal waves only) measurements have been made using a transducer operated at the fundamental frequency of 5 MHz in the temperature range from 150 to 480 K. The elastic moduli, Debye temperature, and Poisson’s ratio have been obtained both as a function of temperature and Bi₂O₃ content. The room temperature study on ultrasonic velocities, attenuation, elastic moduli, Poisson’s ratio, Debye temperature and glass transition temperature show the absence of any anomalies with addition of Bi₂O₃ content. The observed results confirm that the addition of Bi₂O₃ modifier changes the rigid formula character of TeO₂ to a matrix of regular TeO₃ and ionic behaviour bonds (NBOs). A monotonic decrease in velocities and elastic moduli, and an increase in attenuation and acoustic loss as a function of temperature in all the glass samples reveal the loose packing structure, which is attributed to the instability of TeO₄ trigonal bipyramid units in the network as temperature increases. It is also inferred that the glasses with low Bi₂O₃ content are more stable than with high Bi₂O₃ content.     

XAS study of lanthanum coordination environments in glasses of the system K2O---SiO2---La2O3

The La L₁ and L₃ XANES and L₃ EXAFS have been investigated for the series of glasses 10K₂O---50SiO₂---x La₂O₃ (x = 1, 5, 10) and (10 − x)K₂O---40SiO₂−(x/3)La₂O₃ (x = 7.5, 5, 2.5) and model compounds La₂O₃, LaAlO₃, LaPO₄, La₂NiO₄, La₂CuO₄ and La(OH)₃. An edge resonance at 25 eV above the L₁ edge in the glass spectra is concentration-dependent, decreasing in intensity with increasing lanthanum concentration. The 2s → nd forbidden transition increases with La₂O₃ concentration, indicating a reduction in the ‘average’ site symmetry of the first coordination shell of La. Mapping _X(k) space, which is a new and promising technique, was employed to extract bond distance, coordination number and thermal parameters from the EXAFS. By this method, one calculates the complete _X(k) space a function of all physically reasonable values of the adjusted parameters in all possible combinations. The advantage in this method is the assurance of a global minimum. Bond lengths were comparable to those obtained by Fourier transforming the phase corrected EXAFS. The values are 2.42 Å (± 0.03 Å) for La---O. The coordination numbers (N ≤ 7 ± 1.5) were derived by mapping and comparison to the published structures for other La compounds. _X(k) mapping is compared with least-squares fitting the data, and the correlation between the Debye-Waller factor and coordination number is also discussed.     

Glass formation and optical properties of glasses in the systems (R2O or R''O)-Ta2O5---Ga2O3

Gallate glasses containing no conventional glass formers were obtained in the systems (Na₂O, K₂O or Cs₂O)-Ta₂O₅---Ga₂O₃ and (Sr or BaO)-Ta₂O₅---Ga₂O₃ by an ordinary crucible-melting technique. The glasses showed high optical transmission in the infrared as well as in the visible region. Infrared spectroscopic analysis suggested that the Ga³⁺ ions are tetrahedrally coordinated in the glasses. The glass-forming tendency of the melt and the infrared transmission of the glasses are discussed in terms of the glass structure.     

Diffraction studies of rare-earth phosphate glasses

A series of lanthanide oxides was incorporated in a vitreous phosphate host network. Molar constituents of the glasses were typically (La₂O₃)₁₀(R_xO_y)₁₀(Al₂O₃)₅(P₂O₅)₇₅. Each glass had a different lanthanide (R atom) from the series; La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er and the values of x and y depended on the valency of the rare-earth atom. Both X-ray and neutron diffraction were employed in examining their structures. The results indicate that the basic PO₄ tetrahedral unit remains unaltered with an average P–O distance of and predominant Q² linkages to its neighbouring units so as to form a continuous network while accommodating the included lanthanides. In accordance with this model, the average distance of rare-earth (comprising La and a second type of R atom) to oxygen decreased from 2.44 to 2.26 , a trend to be expected from the lanthanide contraction. The average oxygen coordination around the rare-earth was found to vary in the range of 6–8. With these average parameters, a small (74 atom) hand-built model was made to check the feasibility of constructing a continuous random network. Optical transmission measurements show all these glasses to absorb strongly in the UV region and to have marked absorption resonances in the visible region of 400–1000 nm except for the La, Ce, Eu, Tb containing glasses which have low or negligible absorption in the latter range.     

B NMR investigations in xV2O5–B2O3 and xV2O5–B2O3–PbO glasses

11B (I=3/2) MAS NMR in the binary glass system xV₂O₅–B₂O₃ (x=0.053, 0.43) and the ternary glass system xV₂O₅–B₂O₃–PbO (0.1x1.5) has been investigated at room temperature. In the xV₂O₅–B₂O₃ glasses, one NMR line due to BO₃ unit was observed. Meanwhile in the xV₂O₅–B₂O₃–PbO, two NMR lines which arise from BO₃ and BO₄ units were detected, where the appearance of BO₄ units is produced by the presence of PbO. From the computer-simulation of the ¹¹B NMR central transition line (m=−1/2↔1/2), the quadrupole parameters (e²qQ/h and η) for BO₃ units in xV₂O₅–B₂O₃, and those for BO₃ and BO₄ units in xV₂O₅–B₂O₃–PbO were obtained as a function of x. As the V₂O₅ content increases in xV₂O₅–B₂O₃–PbO, the e²qQ/h and η values of the BO₃⁻ associated resonance are found to slightly decrease and increase, respectively. Meanwhile, the e²qQ/h and η values of BO₄⁻ associated resonance in xV₂O₅–B₂O₃–PbO are found to slightly increase and decrease, respectively. By comparing the intensities of the total transitions (m=−3/2↔−1/2,m=−1/2↔1/2, and 1/2↔3/2) for the ¹¹B NMR line of BO₃ and BO₄ units contained in xV₂O₅–B₂O₃–PbO with those of respective standard samples of 0.053V₂O₅–B₂O₃ and NaBH₄, the quantitative fractions of BO₃ and BO₄ in xV₂O₅–B₂O₃–PbO were obtained as a function of x.     

Internal friction in vanadium-phosphate glasses doped with Na2O

The internal friction of _xNa₂O·(0.5−x)V₂O₅·O.5P₂O₅(x = 0.025–0.3) glasses was studied using the low-frequency torsion pendulum technique. The temperature spectrum of internal friction reveals three maxima. Maximum 1, the so-called “electron” maximum, is the same as observed in binary vanadium-phosphate glasses. The origin of maximum 2 can be attributed to ion migration. Maximum 3 appears for glasses containing more than 10 mol.% Na₂O and is probably connected with sodium-proton interactions.     

TOPCon太阳电池发射极Al2O3/SiNx与SiO2/Al2O3/SiNx叠层膜钝化性能的比较

本文对TOPCon电池发射结的叠层钝化膜进行了研究,对比了3种不同叠层钝化膜(SiO₂/SiN_x、Al₂O₃(1.5 nm)/SiN_x、SiO₂/Al₂O₃(1.5 nm)/SiN_x)的钝化性能。结果表明:Al₂O₃(1.5 nm)/SiN_x的钝化性能优于SiO₂/SiN_x,SiO₂/Al₂O₃(1.5 nm)/SiN_x的钝化水平最佳,隐开路电压均值可达到705 mV。基于Al₂O₃/SiN_x叠层膜研究了Al₂O₃厚度(1.5 nm、3 nm和5 nm)对钝化性能和电池转换效率的影响。当Al₂O₃厚度由1.5 nm增加到3 nm时,钝化性能得到明显提升,隐开路电压均值提高了20 mV,达到707 mV,对应电池的光电转换效率升高了0.23个百分点,与SiO₂/Al₂O₃(1.5 nm)/SiN_x叠层膜电池的转换效率持平。然而,当Al₂O₃厚度继续增加至5 nm时,隐开路电压均值保持不变。因此可以使用Al₂O₃(3 nm)/SiN_x叠层膜代替SiO₂/Al₂O₃(1.5 nm)/SiN_x叠层膜,不仅简化了电池的工艺步骤,而且降低了生产成本。     

Glass formation and crystallization in the ZrO2---Al2O3---P2O5 system

The glass formation of the ZrO₂---Al₂O₃---P₂O₅ system in the high phosphate region is determined. The crystallization process and the crystal types formed during heat treatment have been studied. The structure of these glasses is discussed.     

Characteristics of ZnO–B2O3–CaO–Na2O–P2O5 glass powders prepared by spray pyrolysis

Fine-sized ZnO–B₂O₃–CaO–Na₂O–P₂O₅ glass powders with spherical shape were directly prepared by high temperature spray pyrolysis. The ZnO–B₂O₃–CaO–Na₂O–P₂O₅ powders prepared by spray pyrolysis at temperatures above 1200 °C had broad peaks at around 30° in the XRD patterns. The glass transition temperatures (T_g) of the glass powders obtained by spray pyrolysis at preparation temperatures between 900 °C and 1400 °C were near 480 °C regardless of the preparation temperatures. The dielectric layers formed from the glass powders prepared by spray pyrolysis at preparation temperatures above 1300 °C had clean surface and dense inner structure at the firing temperature of 580 °C. The transmittance of the dielectric layer formed from the glass powders obtained by spray pyrolysis at preparation temperature of 1400 °C was 90% at the firing temperature of 580 °C, in which the thickness of the dielectric layer was 13 μm. The UV cutoff edges gradually shift towards longer wavelength with increasing the preparation temperature of glass powders and the firing temperature of dielectric layers.     

A glass-forming system with compound-forming tendency: As4S6---P4S10

Glasses in the quasi-binary system (As₄S₆)_x(P₄S₁₀)_1−x x = 0.1, …, 1.0, are produced and studied by thermal analysis, X-ray, and Raman spectroscopy. The phase diagram of the system and the critical cooling rate for glass formation both have their maximum at x = 0.5, corresponding to the compound As₂P₂S₈; the X-ray structure of recrystallized samples can be described as a sum of the As₂P₂S₈ (x = 0.5)- and the P₄S₁₀-structure (As₄S₆ not visible); Raman spectra of the glasses are again sums of As₂P₂S₈- and As₄S₆/P₄S₁₀-spectra. All these observations support the assumption that a stable building block corresponding to the 1:1 compound As₂P₂S₈ and surplus As₄S₆ (or P₄₁₀) are the essential elements of the structure in the glasses.