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.     

Optical and esr spectra of titanium (III) in Na2O-B2O3 and Na2O-P2O5 glasses

The optical absorption and the esr spectra of titanium(III) in binary Na₂O-B₂O₃ and Na₂O-P₂O₅ glasses have been studied. Titanium(III) produces two optical absorption bands around 20 000 and 14 000 cm^–1 which are assigned to the²B_2g ²B_1g and²B_2g ²A_1g transitions respectively of Ti³⁺ in a tetragonally distorted octahedral environment. The absorption bands in phosphate glasses are narrower and absorption coefficients higher than those in borate glasses. The esr spectrum of titanium(III) in all the glasses consists of a broad asymmetric line withg 1.94 in borate glasses, andg 1.92 in phosphate glasses; no hyperfine structure has been observed.     

Glass transition temperature of glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system

A total of 24 glasses in or near the bioactive region in the system SiO₂-Na₂O-CaO-P₂O₅-Al₂O₃-B₂O₃ were studied. By differential thermal analysis their glass transition temperatures,T _g, were determined. On basis of an experimental plan for 16 glasses, two phenomenological equations describing the relationship betweenT _g and glass composition were developed. The equations describeT _g within the compositional ranges: SiO₂, 38.0–65.5 Na₂O, 15.0–30.0; CaO, 10.0–25.0; P₂O₅, 0–8.0; B₂O₃, 0–3.0; Al₂O₃, 0–3.0 wt%. The glass transition temperature shows a linear dependence of the Na₂O content. The higher the Na₂O content, the lower theT _g. Compositional alterations not including Na₂O influencesT _g little in comparison with changes in the Na₂O content.     

In vivo behaviour of glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system

Sixteen glasses in the SiO₂-Na₂O-CaO-P₂O₅-Al₂O₃-B₂O₃ system were studied. The glasses were implanted in rabbit tibia. According to theirin vivo behaviour, they were divided into five groups. A phenomenological equation for thein vivo behaviour was developed. The solubility of the glasses was determinedin vitro as weight loss in Tris buffer solution. The tissue response is discussed in relation to the glass composition and the solubility. For bone-bonding glasses calcium phosphate formation takes place within a silica-gel at the glass surface. The gel must be sufficiently hydrated and flexible to allow calcium phosphate to build up. The results suggest that alumina can inhibit bone bonding by retarding the formation rate of a silica-rich layer, by stabilizing the silica structure enough to prevent calcium phosphate build-up within the layer, or by either disturbance of the bone mineralization or bone incompatibility of an alumina-containing calcium- and phosphorus-rich surface layer. The mechanism responsible for the lack of bone adherence is determined by the glass composition. Up to about 1.5 wt % Al₂O₃ can be included in the glass without destroying the bioactivity.     

Preparation and magnetic properties of SiO2-CaONa2O-P2O5-FeO-Fe2O3glass-ceramics prepared by gel-melt method

The SiO2-CaO-Na2O-P205-FeO-Fe2O3 precursors were prepared by the sol-gel method.And then two different ways were used to obtain the ferrimagnetjc glass-ceramics,j.e.,one is compression-sintering method.and the other is melt-quenching-heat treatment.The crystalline type and size of the magnetite were analyzed by XRD patterns.and the magnetism of samples were characterized by VSM.This kind of glass-ceramics shows a bioactive behavior after soaked in the Simufated body fluid test for two weeks.     

掺Sm2O3的P2O5-BaO-Al2O3玻璃的形成及部分光学性能

随着信息技术、激光技术和军事技术的快速发展,各种功能玻璃材料的研究受到了科研工作者的极大关注。采用两步熔融法观察了空白试样和掺加Sm2O3 的玻璃形成区,结果表明随着稀土含量的增加,形成区缩小,Sm2O3 的含量不能>15%mol;通过红外光谱仪和分光光度计研究了玻璃的结构和吸收谱线,结果显示:随 Al2O3 含量增加,[PO3-4 ]基团的振动特征吸收峰逐渐缩小直至消失,同时随稀土含量的增加出现尖锐的P—O—Sm键振动吸收峰;吸收光谱中吸收峰强度随稀土含量增加逐步增强,透过率下降。     

Structural and electrical characteristics of Sr(Fe2/3W1/3)O3 ceramics

The polycrystalline samples of Sr(Fe_2/3W_1/3)O₃ (SFW) were prepared by a high-energy ball-milling followed by solid-state reaction technique. The X-ray structural analysis showed the formation of single-phase compound in the tetragonal system, which is a distorted structure of an ideal cubic perovskite. The temperature–frequency dependence of dielectric constant and loss tangent exhibited relaxation behavior of the compound. The studies of impedance parameters (Z′, Z″) as a function of temperature and frequency have confirmed the contribution of bulk resistance of SFW. The small value of activation energy of the compound (～ 0.35 eV) can be explained by mixed ionic–polaronic conductivity mechanism.     

Non-adiabatic polaron hopping conduction in semiconducting V2O5-Bi2O3 oxide glasses doped with BaTiO3

BaTiO₃-doped (5–40 wt %) 90V₂O₅-10Bi₂O₃ (VB) glasses have been prepared by a quick quenching technique. The d.c. electrical conductivities, _d.c., of these glasses have been reported in the temperature range 80–450 K. The electrical conductivity of these glasses, which arises due to the presence of V⁴⁺ and V⁵⁺ ions, has been analysed in the light of the small-polaron hopping conduction mechanism. The adiabatic hopping conduction valid for the undoped VB glasses (with 80–95 mol % V₂O₅), in the high-temperature region, is changed to a non-adiabatic hopping mechanism in the BaTiO₃-doped VB glasses. At lower temperatures, however, a variable range hopping (VRH) mechanism dominates the conduction mechanism in both the glass systems. Such a change-over from adiabatic to non-adiabatic conduction mechanism is a new feature in transition metal oxide glasses. Various parameters, such as density of states at the Fermi level N(E_F), electron wave-function decay constant, , polaron radius, r _p, and its effective mass, m _p ^* , etc., have been obtained for all the glass samples from a critical analysis of the electrical conductivity data satisfying the theory of polaron hopping conduction.     

Photoluminescence of Ti3+ in P2O5-Na2O-Al2O3 glass

The optical properties (absorption and luminescence) of Ti³⁺ in a P₂O₅ Na₂O-Al₂O₃ glass have been studied in the temperature range 12 to 300 K. A very broad infrared emission band at 860 nm, has been observed for the first time in an inorganic glass, when excitation is performed in the Ti³⁺ absorption band (T_2g → E_g transition in cubic field approximation). The spectroscopic characteristics of this system are compared with those of the Ti³⁺ as a dopant in AL₂O₃ single crystals.     

Ac conductivity of BaTiO3 containing (90V2O5-10P2O5) oxide glasses dispersed with nanocrystalline particles

The frequency dependent AC conductivity (_ac) of some new multicomponent (1 – x) (90V₂O₅-10P₂O₅) + xBaTiO₃ (x = 0.1 to 0.9) type glasses containing nanocrystalline BaTiO₃ particles (observed from the transmission electron microscopic study) has been reported in the temperature range 80–400 K. The behavior of _ac is broadly similar to what has been observed previously in many other amorphous semiconductors and polymers (namely nearly linear frequency dependence and weak temperature dependence). Analysis of the experimental conductivity data shows that Long's overlapping large polaron tunneling (OLPT) mechanism is the most probable mechanism of conduction for the present BaTiO₃ doped glasses. The Quantum mechanical tunneling (QMT) model and the classical hopping of electrons over a barrier can, however, explain the AC conductivity data only below _D/2–160 K (_D is the Debye temperature). Reasonable values of the relaxation time and barrier heights related to the models have been obtained from the fits of the conductivity data.     

Oxygen ionic conduction in Y2O3-stabilized Bi2O3 and ZrO2 composites

Oxygen-ion conductivity was measured in two-phase mixed composites in the system f c c Bi₂O₃ (BY)-fcc ZrO₂ (ZY) stabilized with Y₂O₃ (Y = 20 at%). The composites appeared in the range 0.02 < × < 0.90 for BY_xZY_1-x (mole fraction). Conductivity decreased with increasing ZY concentration. The composition dependence of conductivity could be explained by using an effective-medium approximation, although the conductivity was slightly higher than the calculated value in specimens containing ZY above 50 vol %.     

Effect of annealing on the electrical and optical properties of V2O5-GeO2 glasses

Increases in the electrical conductivities of vanadium germanate glasses on annealing have been reported recently in the literature. The increases were attributed to the formation of microstructure on annealing. In the present work we report a study of the V₂O₅-GeO₂ glass system using electron paramagnetic resonance, optical absorption, differential scanning calorimetry and electron diffraction techniques. The V₂O₅-GeO₂ glass system consists of an equimolar mixture of vanadium pentoxide and germanium dioxide. One sample was unannealed and the other was annealed at 300° C for about 24 h. The results revealed that the increase in the electrical conductivity of the annealed samples could be attributed to the increase of reduced valence states of vanadium ions which accompany the microstructure formation and not solely to the structural change. Afzal Sheikh in electron diffraction studies is appreciated.