稀土对BaTiO_3陶瓷的气相化学热扩渗及其电性能研究

Studies of Gas Thermochemical Penetrating of Rare Earthto BaTiO_3 Ceramics and Their Electric Characteristics

采用气相法对钛酸钡陶瓷扩渗稀土元素,稀土扩渗使BaTiO3陶瓷的电性能发生了显著变化。室温电阻率明显下降,从4.3×109Ω·m变为4.84Ω·m;随着频率增大和温度升高,交流电导逐渐增大,BaTiO3陶瓷的导电性更强。稀土扩渗使BaTiO3陶瓷的介电常数明显增加,尤其在低频下增加显著;介电常数随温度的变化呈明显的PTC效应,并使BaTiO3陶瓷的居里温度升高为124.9℃。经XRD分析,扩渗的稀土元素并没有进入BaTiO3陶瓷的晶格中,而是存在于晶界上。经XPS测试分析,稀土扩渗后的BaTiO3陶瓷中钡、钛、稀土等都存在着不同程度的变价,因而导致了BaTiO3陶瓷电阻率的降低。TG-DTA曲线分析表明,稀土扩渗后的BaTiO3陶瓷有较好的高温热稳定性。

The penetrating of rare earth to BaTiO3 ceramics in gas phase was reported for the first time. The penetrating conditions and effects on electric characteristics of BaTiO3 ceramics were studied. The results showed that the penetrating of rare earth made the electric characteristics changed obviously. The resistivity of BaTiO3 ceramics penetrated with rare earth decreased obviously, when the rare earth content was 2% (wt), the penetrating temperature was 860degreesC and the penetrating time was 4h, the resistivity decreased to the smallest, which changed from 4.3 x 10(9) Omega (.) m to 4. 84 Omega (.) m, and the conductance increased with the increasing of frequency and temperature, the electrical conductivity was better. The constant (epsilon) of BaTiO3 ceramics penetrated with rare earth increased visibly, especially at lower frequency, the constant exhibited PTC effect, and the Curie-temperature (T-c) had gone up to 124.9degreesC. It was showed through XRD analysis that the penetrated rare earth was entered into the grain boundary. Through X-ray photoelectron spectrum, the binding energy of the elements were analyzed, which indicated that the quantivalence of barium, titanium and rare earth in BaTiO3 ceramics were variable, and resulted in the improving of the conductibility of BaTiO3 Ceramics. The results of TG-DTA analysis showed that the thermal stability in high temperature of BaTiO3 ceramics penetrated with rare earth was better.