Some physical properties of V2O5-Fe2O3 and V2O5-Fe2O3-Li2O systems

Various methods have been used to study the physical properties of the V₂O₅-Fe₂O₃ and V₂O₅-Fe₂O₃-Li₂O systems, including X-ray, electron microscope, Mössbauer effect, NMR and thermogravimetric measurements. The iron ions are approximately equally distributed in substitutional and interstitial sites in the V₂O₅ lattice. The maximum number of iron ions dissolved in the V₂O₅ matrix corresponds to 4 mol % Fe₂O₃. In all the samples a quantity of Fe₂O₃ which has not been included in lattice is observed. The V₂O₅-Fe₂O₃ and V₂O₅-Fe₂O₃-Li₂O systems are formed from solid solutions mixed with very small Fe₂O₃ particles. The analysis of the charge compensation of iron ions suggests that V₂O₅ is a quasi-amorphous semiconductor. Irradiation of V₂O₅-based samples with an electron beam induces the V₂O₅ platelets to convert to the VO _x phase.     

Structural studies of some V2O5-P2O5-B2O3-Fe2O3 glass systems

X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass containing different amounts of iron ranging from 0–7.5 mol % and heat treated at 300 °C for various times. The structure and phase separation could be determined for each glass composition. V₂O₅ was the main precipitated phase in all heat-treated samples, and its amount was dependent on the heat-treatment time and Fe₂O₃ content. Also FeP was detected in samples heat treated for 24 h. The infrared measurements showed the presence of both V⁴⁺ and V⁵⁺. The symmetry of V₂O ₇ ⁴⁻ and VO ₄ ³⁻ groups was found to increase with increasing Fe₂O₃ content. It was also found that some PO₄ changed to BO₃, forming a non-bridging oxygen.     

Plasma spraying of Al2O3 and Al2O3Y2O3

A microstructural study has been carried out of plasma-sprayed Al₂O₃ and mixed and sintered Al₂O₃Y₂O₃. In order to ascertain the degree of metastability achieved by plasma spraying, these results are compared with a similar experiment utilizing a CO₂ laser for melting and the hammer-and-anvil technique for quenching of the same materials. X-ray diffraction methods were used to determine the obtained phases and crystal structures. In addition, transmission electron microscopy was used to confirm the phases present and to study their morpology. The porosity was studied with both mercury intrusion porosimetry and small angle neutron scattering. The addition of Y₂O₃ is shown to decrease the porosity from 15% to 7.5%. Adhesion is likewise related to the addition of Y₂O₃ and it is seen that adhesion of the mixture is measurably improved over that of pure Al₂O₃. The implication of these results is discussed.     

Study of structures and properties of ZnO-Sb2O3-P2O5-Na2O glasses

The influence of ZnO substitution by 0–12 wt.% Na₂O on the properties of ZnO-Sb₂O₃-P₂O₅-Na₂O glasses has been investigated. The structure and properties of the glasses with the composition of (13.86-x)ZnO-57.93Sb₂O₃-28.21P₂O_5?x Na₂O (x = 0–12 wt.%) were characterized by infrared spectra (IR), X-ray diffraction and differential thermal analysis (DTA). The results of IR indicated an increase in the intensity of symmetric vibrations of P-O-P bond, which was confirmed by the improvement of water durability with the increasing amount of Na₂O in the range of 0–10 wt.%. Substitution of 10 wt.% Na₂O led to the weight loss of the glass to 5.93 mg/cm^?2 after immersion in deionized water at 50 °C for 24 h. The results of XRD showed that the ability of crystallization decreased, indicating the good thermal stability of the glass. The glass containing 8 wt.% Na₂O had the best properties in every respect and might be an alternative to lead based glasses for the applications, providing further composition improvement.     

Crystallization and properties of CaO-P2O2-B2O3 glasses

Glasses were prepared with compositions (50–0.5 x) CaO.(50–0.5 x) P₂O₅ · x B₂O₃ with B₂O₃ contents (x) from 0 to 45 mol%. The glass transformation temperature (T _g), dilatational softening temperature (T _D) and Vickers hardness (H _V) initially increased with x, but showed maxima at about x=20 for T _g and T _D and at about x=35 for H _V. The thermal expansion coefficient decreased with x, levelling off at about 35 mol% B₂O₃. The maximum tendency to crystallize occurred at around 25 mol% B₂O₃. Volume nucleation (and hence glass-ceramic formation) and surface nucleation were obtained for x between 15 and 25 mol%. The first phase to appear was BPO₄, which was probably homogeneously nucleated. Subsequently the 4CaO · P₂O₅ phase was heterogeneously nucleated on the BPO₄. For 10 x 35 only surface nucleation was observed. The kinetics of nucleation were investigated in the 20 mol% B₂O₃ glass. The changes in properties and crystallisation behaviour with B₂O₃ content were related to short-range structural information. Infrared spectra and literature data indicated a threedimensional network of B-O-B and B-O-P linkages in the glasses.     

Microstructure and Strength of Al2O3/Al2O3 Joints Bonded with ZnO-Al2O3-B2O3-SiO2 Glass-Ceramic

ZnO-Al2O3-B2O3-SiO2 （ZABS） glass powder was used as interlayer to join alumina ceramics. The effect of joining temperature on the microstructure and strength of joints was investigated. The results showed that the ZABS glass can react with alumina substrate to form a layer of ZnAl2O4 at Al2O3/glass interface. Bending test exhibited that low joining temperature （1150℃） led to low joint strength due to the formation of pores in the interlayer, originated by high viscosity of the glass. High joining temperature （1250 ℃） also resulted in low joint strength, because of large CTE （coefficient of thermal expansion） mismatch between amorphous interlayer and alumina substrate. Therefore, only when the joining temperature was appropriate （1200℃）, defect-free interface and high joint strength can be obtained. The optimum joint strength reached 285 MPa, which was the same as the base material strength.     

The effect of V2O5 on the sintability and physical properties of Bi2O3-NiO-Nb2O5 and Bi2O3-ZnO-Nb2O5 temperature-stable dielectrics

The sintering temperature of the bismuth-based temperature-stable dielectrics (BNN-BZN) is reduced down to 850 °C with 1.0 wt % of V₂O₅, which is the lowest to our knowledge. The effect of dopant is studied in detail. The V₂O₅ seems to provide an eutectic melt below the sintering temperature to increase the sinterability. A composite character was observed with 1.0 wt % of V₂O₂ doping, while a new solid-solution phase was found without or fewer amounts of additive. Nevertheless, the obtained physical property of the sample with 1.0 wt % of V₂O₅ is promising. Following combination of physical properties is obtained consistently without any quenching procedure; dielectric constant >95, Q 2000, T.C. = –8.6 ppm (30–100 °C), and specific resistivity = 10¹² cm.     

Physical and Thermal Properties of P2O5-Al2O3-BaO-La2O3 Glasses

The physical and thermal properties of P2O5-Al2O3-BaO-La2O3 glasses were investigated. The effects of glass compositions on the transition temperature, thermal expansion coefficient, density, hardness and refractive index of glasses were studied. The highest hardness of the glasses is 4143.891 MPa and the lowest thermal expansion coefficient of the glasses is 71.770×10-7/℃. A phosphate glass with high mechanical strength and good thermal characteristic is obtained.     

Surface tension of PbO-B2O3 and Bi2O3-B2O3 glass melts

The surface tensions of xPbO-(100?x) B₂O₃ (x = 30–80 mol%) and xBi₂O₃-(100?x) B₂O₃ (x = 0–100 mol%) melts were measured using the ring method over the temperature range 973 to 1373 K. The compositional and temperature dependences of surface tension were investigated. Addition of PbO and Bi₂O₃ to B₂O₃ increased the surface tensions of their respective PbO-B₂O₃ and Bi₂O₃-B₂O₃ melts. The surface tension showed a maximum at 60 mol% PbO in the PbO-B₂O₃ melts and at 70–80 mol% Bi₂O₃ in the Bi₂O₃-B₂O₃ melts. The temperature coefficient of surface tension was examined on the basis of its relationship to the structure, and it was suggested that the temperature coefficient of surface tension decreases with an increasing content of four-coordinated boron.     

Preparation of pressureless-sintered SiC-Y2O3-Al2O3

Sintering additives were prepared from aluminium hydroxide and yttrium hydroxide. These additives were soluble in water and resulted in a binder. A -SiC powder was mixed with the additive solution and sintered at 2150° C without pressure. The oxides formed from the additive promoted sintering. The sintered body contained no pores. Aluminium, silicon, and yttrium oxide were precipitated in the sintered body.     

掺铒Bi2O3-GeO2-Ga2O3-Na2O玻璃中激发态吸收的抑制

对应用于1.55μm波段宽带放大的掺Er3 :Bi2O3-GeO2-Ga2O3-Na2O(玻璃中激发态吸收的抑制进行了研究.为此,在该玻璃中分别引入了Ce3 离子和B2O3组分.研究表明,随着玻璃中Ce2O3的掺杂或B2O3组分的引入, Er3 4:I11/2能级与Ce3 2:F5/2能级间的能量传递或Er3 4:I11/2→4I13/2能级间多声子弛豫速率相应提高, Er3 离子4I11/2能级荧光寿命显著减小,激发态吸收得到有效抑制.同时,实验发现, Ce2O3的掺杂进一步提高了Er3 离子4I13/2→415/2能级间总量子效率,增强了1.55μm波段荧光发射强度,而荧光发射谱宽基本保持不变. B2O3组分的引入虽在一定程度上削弱了1.55μm波段荧光发射强度,但进一步拓展了其荧光发射谱,且增益截面峰值波长移向长波段.     

Nb_2O_5对碲铅铋铌系玻璃结构和性能的影响

采用熔融法制备不同Nb2O5含量的TeO2-PbO-Bi2O3-Nb2O5系玻璃粉,研究了Nb2O5的加入量对TeO2-PbO-Bi2O3-Nb2O5系玻璃热膨胀系数、软化温度和热稳定性的影响。利用傅里叶变换红外光谱仪检测玻璃粉的结构,通过热机械分析仪和综合热分析分别测试玻璃的膨胀系数和析晶温度,采用场发射扫描电镜观察太阳能电池Ag/Si接触界面。结果表明,随着Nb2O5含量的增加,玻璃的热膨胀系数和软化温度逐渐降低,玻璃化温度和析晶温度逐渐升高,玻璃的热稳定性逐渐增强。添加Nb2O5的玻璃粉所对应的太阳能电池正面电极中,Ag/Si接触界面存在大量的纳米银粒子,这将更有利于晶硅太阳能电池的光电子传导。