KNb_(1-x)Ti_xO_(3-δ)固溶体的合成与表征

Synthesis and Characterization of KNb_(1-x)Ti_xO_(3-δ) Solid Solutions

利用高温高压法首次合成了KNb1 -xTixO3-δ(x =0～ 0 .4)系列固溶体 ,并使用X射线衍射、TG DTA、Raman谱和交流阻抗谱等对样品的结构、热稳定性和导电性进行了表征。XRD结果表明 ,随掺杂量的增加 ,晶胞体积减小 ;Ti掺杂引起了固溶体结构的转变 ,x <0 .1 5的样品为正交钙钛矿结构 ,而x≥ 0 .1 5的样品几乎为纯四方相结构。Raman谱和DTA结果显示 ,Ti掺杂使四方相区宽化 ,并且随掺杂量的增加 ,相变温度逐渐下降。阻抗谱测量表明 ,所有样品均以离子导电为主 ,其中KNb0 .85Ti0 .1 5O2 .92 5的氧离子导电率最高 ,在 80 0℃时达到 5 .6× 1 0 - 3S·cm- 1 ,在测量温度范围内 ,电导率可以拟合成两条直线 。

KNb 1-xTi xO 3-δ (x=0～0.40) solid solutions were synthesized under high temperature and high pressure for the first time. The structural characteristics and ionic conductivity of KNb 1-x·Ti xO 3-δ solid solutions were investigated by XRD,TG-DTA,Raman and impedance spectroscopy techniques. XRD results showed that Ti-doping resulted in structural transformation, the samples of x<0.15 have orthorhombic perovskite structure, but the samples of x≥0.15 are single tetragonal phase.With the increase of doping amount,the cell volume decrease.The Raman spectra at different temperatures and DTA curve indicate that the structure of the solid solutions had been changed,Ti-doping broadens tetragonal phase zone,and curie temperature decrease with the increase of dopant content. The ionic conductivity of the samples measured by impedance spectroscopy shows that in all the samples the ions are main carriers.KNb 0.85Ti 0.15O 2.925 has the highest conductivity of 5.6×10 -3S·cm -1 at 800 ℃. A marked curvature at T=630 ℃ has been observed in the Arrhenius plot of the bulk conductivity.The activation energy below 630 ℃ is lower than that above 630 ℃,and the cause is discussed.