Y2O3掺杂CaO-Al2O3-SiO2系微晶玻璃的研究

在CaO-Al2O3-SiO2(CAS)系统微晶玻璃中引入稀土氧化物Y2O3,结合XRD、SEM等测试手段,研究了Y2O3的引入对微晶玻璃烧结过程、微观结构以及性能的影响。实验结果表明:随着Y2O3的引入,微晶玻璃烧结温度降低,烧结时间变短。当Y2O3质量分数为3.25%时,CAS微晶玻璃具有最佳的制备工艺和最好的力学性能。     

Gd2O3掺杂对BaTiO3陶瓷电性能的影响

采用溶胶-凝胶法制备了掺杂不同量Gd2O3(分别为0 001、0 002、0 003、0 005、0 007mol mol)的BaTiO3陶瓷,并对其电性能进行了研究。结果表明:Gd2O3掺杂使BaTiO3陶瓷的电阻率明显下降,当添加量为0 002mol mol时,电阻率最小,为1 27×105Ω·m;晶粒电阻随着温度的变化,呈现NTC效应,而晶界电阻随着温度的变化,呈现PTC效应,而且晶界电阻远远大于晶粒电阻,说明Gd2O3掺杂BaTiO3陶瓷的PTC效应是一种晶界效应;Gd2O3掺杂使BaTiO3陶瓷的介电常数和介电损耗在低频时明显增大,在高频时又明显降低。     

Al2O3掺杂YSZ的电性能

研究了Al2O3掺杂对Y2O3稳定的ZrO2材料电导性能的影响。因为Al与自由氧离子空穴缔合的能力大于Y，所以YSZ的晶粒电导随Al2O3含量的增大而减小。Al2O3一方面能清除晶界上的SiO2，同时又与晶界中的氧离子空穴缔合，在这两方面影响下，随Al2O3含量的增大，晶界电阻先减小后增大。     

SiO2掺杂对ZnO-Bi2O3基压敏陶瓷微观结构及电性能的影响

采用传统固相法成功制备了不同SiO2掺杂量的ZnO-Bi2O3基压敏陶瓷.研究了SiO2添加剂对ZnO-Bi2O3基压敏陶瓷物相组成、微观形貌和电性能的影响规律及作用机理.XRD结果表明,ZnO-Bi2O3基压敏陶瓷由ZnO主晶相和尖晶石相、富Bi相和含Si相等第二相组成.当SiO2含量增加时,ZnO晶粒尺寸逐渐减小,...     

掺杂对ZnO压敏陶瓷电性能的影响及其应用

ZnO压敏陶瓷具有优良的电流-电压非线性和冲击能量吸收能力、低漏电流和低成本,广泛用于电力系统和电子线路等领域。介绍了掺杂改性对ZnO压敏陶瓷电性能的影响,最后介绍了ZnO压敏陶瓷的应用。     

Y3+掺杂对Al2O3陶瓷硬度的影响

本实验主要研究了稀土Y2O3添加量、成形压力和烧结温度等对氧化铝陶瓷的影响.研究结果表明,在Y2O3掺量为0.5wt%、压力20MPa和1 600℃烧成(保温2h)的条件下,Al2O3陶瓷的密度可达3.9g/cm3以上,其硬度也得到了很大程度的提高.微观结构分析表明,添加Y2O3不仅可以细化晶粒,还能抑制氧化铝晶粒的异常长大,使晶粒尺寸均匀而形成致密化结构.     

掺杂Y2O3对钛酸锶钡陶瓷微观结构和介电性能的研究

用固相法制备了制备Ba0.75 Sr0.25 TiO3陶瓷.研究发现,当Y2 O3掺杂量在0.8％以内时,样品均为四方钙钛矿结构.同时,适量的Y2O3掺杂有利于提高材料的介电常数,降低材料的介电损耗.当烧结温度为1260℃,Y2O3掺杂量为0.1％时,BST的样品的相对密度为95.4％,介电常数达最大值,为4730,其介质损耗为0.00237.而Y2O3掺杂量为0.6％时样品的高频稳定性较好.     

掺杂Y2O3对BaZr0.1Ti0.9O3陶瓷电介质性能的影响

研究了掺杂量不同的Y2O3对BaZr0.1R.9O3微观形貌及介电性能的影响.实验发现:通过XRD物相分析,所有试样均形成典型的钙钛矿结构的主晶相,说明钇掺杂并未改变锆钛酸钡的晶型结构.一定量的Y2O3可抑制晶粒的长大,使晶粒细化,降低气孔率,试样得到致密化.当Y2O3的掺入量为0.05mol％时,试样的介电损耗最小.Y2O3掺杂可提高锫钛酸钡陶瓷居里点处的介电常数,展宽介电温谱,提高材料的实际应用性.     

ZnO含量对Tb3+掺杂ZnO-B2O3-SiO2玻璃余辉性能及光致变色的影响

选择制备了Tb3+掺杂的不同ZnO含量、组成为xZnO- [(100-x)/2]B2O3-[(100-x)/2]SiO2(x=55,60, 65,70)的ZBS玻璃.并通过光致发光光谱、余辉衰减曲线、热释光谱以及紫外-可见吸收光谱系统地研究了该玻璃系统的余辉发光特性和光致变色现象.随着ZnO含量的增加,基质玻璃中Tb3+的5D4→7F5跃迁对应的余辉发光强度增大、其寿命变长.热释光谱表明ZnO含量的提高没有形成新的陷阱,而是增加了陷阱的浓度导致余辉寿命增长.光致变色实验发现:不同样品在紫外照射后其变色程度随ZnO含量增加而增加.玻璃的变色主要由色心引起,本研究中ZnO含量的增加使玻璃基质中Zn离子相关的氧空位浓度增大,从而在紫外光照射后,具有不同陷阱能级深度的色心浓度也相应增加,最终导致了所观察到的余辉特性和光致变色特性的变化结果.另外,通过对不同温度热处理后样品的透过率变化实验分析认为,陷阱能级浅的色心对长余辉有贡献,能级深的将稳定存在于基质中,并对光致变色有较大贡献.     

Y2O3-Bi2O3可见光催化降解甲基橙

采用固相合成法制备了Y<,2>O<,3>-Bi<,2>O<,3>复合可见光催化剂,用XRD、DRS对复合催化剂进行了表征.以甲基橙为模拟废水,在日光色镝灯光照下,研究了废水浓度、催化剂投加量、温度、pH等对Y<,2>O<,3>-Bi<,2>O<,3>光催化活性的影响.实验结果表明:在甲基橙质量浓度为20 mg/L、Y<...     

Characteristics of ZnO-based varistor ceramics doped with Al2O3

The influence of Al₂O₃ doping in the range 0.00–0.83 mol% on the microstructure and current–voltage characteristics of ZnO-based varistor ceramics sintered at 1200 °C for 2 h was studied. The threshold voltage V_T (V/mm) increased up to a dopant level of about 0.08 mol% Al₂O₃; the nonlinear coefficient α was significantly increased by additions of up to 0.04 mol% Al₂O₃, although larger additions of Al₂O₃ caused it to decrease; and the leakage current increased sharply with increasing amounts of Al₂O₃. Doping with Al₂O₃ up to about 0.12 mol% Al₂O₃ resulted in a significantly decreased ZnO grain size, which is mainly responsible for the significantly increased threshold voltage, V_T. No ZnAl₂O₄ spinel phase was detected in any of the samples, and EDXS and WDXS analyses showed that most of the added Al₂O₃ distributed between the Zn₇Sb₂O₁₂ spinel phase and the ZnO phase, while only trace amounts were detected in the Bi₂O₃-rich phase. The spinel phase incorporates an appropriate amount of Al₂O₃; however, with an increasing amount of added Al₂O₃, more of it remains outside the spinel phase in the Bi₂O₃-rich liquid, where it can incorporate into the growing ZnO grains at the sintering temperature. The amount of Al in the ZnO grains was determined. A mechanism for the grain growth inhibition resulting from the small amounts of Al₂O₃ in the Bi₂O₃-rich liquid phase is also proposed.     

Microstructure and electrical properties of rare earth doped ZnO-based varistor ceramics

ZnO-based varistor ceramics doped with Nd₂O₃ and Y₂O₃ have been prepared by the conventional ceramics method. The phase composition, microstructure and electrical properties of the ceramics have been investigated by XRD, SEM and a V–I source/measure unit. The XRD and EDS analyses show the presence of ZnO, Bi₂O₃, Zn₇Sb₂O₁₂, Y₂O₃, Nd-rich phase and Y-containing Bi-rich phase. The electrical properties analyzed show that the nonlinear coefficient of the varistor ceramics is in the range of 4.4–70.2, the threshold voltage is in the range of 247.1–1288.8 V/mm, and the leakage current is in the range of 1.51–214.6 μA/cm². The 0.25 mol% Nd₂O₃ added varistor ceramics with 0.10 mol%Y₂O₃ sintered at 1050 °C exhibits excellent electrical properties with the high threshold voltage of 556.4 V/mm, the nonlinear coefficient of 61 and the leakage current of 1.55 μA/cm². The results illustrate that doping Nd₂O₃ and Y₂O₃ in ZnO-based varistor ceramics may be a very promising route for the production of the higher threshold voltage and the nonlinear coefficient of ZnO-based varistor ceramics.     

Effect of Al2O3 on the microstructure and electrical properties of WO3-based varistor ceramics

The influence of Al₂O₃ additive on the electrical properties and microstructure of (Na,Mn)-doped WO₃ ceramics was studied. Addition of Al₂O₃ shifts the current–voltage characteristics to higher fields and inhibits the grain growth of the WO₃-based non-Ohmic ceramics. The non-linearity coefficient of the current–voltage characteristics of the Al₂O₃-doped WO₃ ceramics increases with sintering temperature and attains a maximum value at 1250°C.     

Influence of Ca-doping on the nonlinear properties of novel ZnO-Cr2O3-based varistor ceramics

The influence of Ca-doping on the microstructure development and electrical characteristics was studied in the novel, ZnO-Cr₂O₃-based, varistor ceramics with the nominal composition (99.47-x) mol% ZnO + 0.1 mol% Cr₂O₃ + 0.33 mol% Co₃O₄ + 0.1 mol% La₂O₃ + x mol% CaCO₃, with x ranging from 0 to 6, sintered at 1200 °C. The results showed that, within the limits of the solid solubility of CaO in ZnO, the addition of CaO greatly enhanced the diffusion processes and hence the grain growth, thus broaden the range of breakdown voltages. Moreover, the Ca-doping simultaneously increases the height of the electrostatic Schottky barrier, resulting in a higher nonlinear coefficient of 40 and a lower leakage current of 2.8 μA/cm². The results are important for the potential application of these novel ZnO-Cr₂O₃-based varistors, having different nominal voltages and yet suitable dimensions, in overvoltage protection across a broad range of voltages.     

Shock-sintering of low-voltage ZnO-based varistor ceramics with Bi4Ti3O12 additions

Microstructure development in ZnO ceramics with Bi₄Ti₃O₁₂ (BIT) additions was studied in dependence of sintering temperature, inversion boundary (IBs) nucleation, heating rate and doping with transition metal oxides (NiO, MnO₂ and Co₃O₄). We demonstrated that one of the essential conditions for homogeneous microstructure development in this system is rapid release and efficient distribution of TiO₂, necessary for the formation of Ti-rich (tail-to-tail) IBs in ZnO grains. This can be achieved via the so-called shock-sintering procedure described in this article. Immediate decomposition of BIT to TiO₂-rich Bi₂O₃ liquid phase above 1200 °C leads to nucleation of ZnO grains with IBs. Exploiting the growth of ZnO grains with IBs, microstructure development can be easily controlled via the IB-induced grain growth mechanism, previously described in SnO₂-doped and Sb₂O₃-doped ZnO. In contrast to conventional sintering, where erratic nucleation of IBs leads to bimodal grain size distribution, shock-sintering sintering regime produces microstructures with uniform coarse-grain sizes, required for low-voltage varistor ceramics.     

Influence of sintering on microstructure and electrical properties of ZnO-based multilayer varistor (MLV)

The effect of sintering on microstructure, dielectric property and varistor property of ZnO-based multilayer varistor (MLV) were investigated. The results show that an optimum microstructure of ZnO-based MLV can be obtained when sintering at 950 °C/1.5 h. The reaction between ZnO and Sb₂O₃ is noted. Also, the segregation of Bi₂O₃ to the inner electrode and thus the reaction of Bi₂O₃ with Pd are observed. The V_B and α value of ZnO-based MLV can be controlled in a straightforward manner through the control of grain size. The decrease in V_B directly relates to the grain growth of ZnO grains when increasing the sintering temperatures from 900 to 1050 °C. Moreover, the increase of capacitance with sintering temperature may mainly result from the coalescence of ZnO matrix grains. The energy absorption capabilities in terms of electro-static discharge (ESD) and peak current (PC) measurements of ZnO-based MLV are reported. The optimum varistor properties of ZnO-based MLV can be obtained when sintering at 950 °C.     

Influence of Bi2O3/TiO2, Sb2O3 and Cr2O3 doping on low-voltage varistor ceramics

The influence of the amount of Bi₂O₃ and TiO₂ additions at a TiO₂/Bi₂O₃ ratio of 1, as well as Sb₂O₃ and/or Cr₂O₃ doping, on the microstructural development and electrical properties of varistor ceramics in the ZnO–Bi₂O₃–TiO₂–Co₃O₄–Mn₂O₃ system was investigated. In samples with a low level of Bi₂O₃ and TiO₂ (0·3 mol%) and therefore small amount of liquid phase, exaggerated growth of the ZnO grains results in high microstructural inhomogeneity. Co-doping with Sb₂O₃ significantly changes the phase composition of TiO₂ doped low-voltage varistor ceramics. The Bi₃Zn₂Sb₃O₁₁ type pyrochlore phase forms at the expense of the γ-Bi₂O₃ and Bi₄Ti₃O₁₂ phases and decreases the amount of liquid phase in the early stages of sintering. Already small amounts of Sb₂O₃ and/or Cr₂O₃ added to a TiO₂ doped low-voltage varistor ceramics limit ZnO grain growth and increase the threshold voltage V_T of the samples.     

Electrical properties and stability of praseodymium oxide-based ZnO varistor ceramics doped with Er2O3

The electrical properties and its stability against DC accelerated aging stress of Pr₆O₁₁-based ZnO varistor ceramics were investigated with Er₂O₃ content and sintering time. The nonlinear exponent of varistors with increasing Er₂O₃ content varied with V-shape, reaching minimum at 1.0 mol% Er₂O₃. As sintering time is increased, the nonlinear exponent was decreased, whereas its stability for DC stress was improved. The varistor with 0.5 mol% Er₂O₃ sintered at 1340 °C for 2 h exhibited the best performance for the nonlinearity and stability. This varistor exhibited not only high nonlinearity, with the nonlinear exponent of 43.4 and the leakage current of 1.2 μA, but also high stability, with the variation rates of varistor voltage and nonlinear exponent is −1.5 and −2.5%, respectively, under DC stress, such as (0.80V_{1 mA}/90 °C/12 h)+(0.85V_{1 mA}/115 °C/ 12 h)+(0.90V_{1 mA}/120 °C/12 h)+(0.95 V_{1 mA} /125 °C/12 h) +(0.95V_{1 mA}/150 °C/12 h).     

Structure and electrical properties of polymer composites based on tungsten oxide varistor ceramics

Composites based on nonlinear tungsten oxide ceramics and a polyethylene matrix with a volume fraction of ceramic filler from 10 vol % to 43 vol % were studied. It was shown that composites are an isotropic mixture of WO₃ grains in a polymer matrix. The current-voltage characteristics of the composites were nonlinear. Composites have a high positive temperature coefficient of resistance up to 15.8 K^-1 in the temperature range of 40–75 °C. It is shown that the temperature coefficient of resistance is positive and increases with increasing electric field strength. The decrease in the electrical conductivity of composites with increasing temperature is explained by the expansion of the polymer matrix and the rupture of the current-conducting channels between the conducting grains of the varistor ceramics. The dependence of the electrical conductivity of the composite on the volume fraction of varistor ceramics is well described within the framework of a three-dimensional percolation model for a two-phase system.