混合氧离子导体BaCo_(0.2)Fe_(0.6)Ti_(0.2)O_(3-δ)的制备与性能研究

Preparation, electrical and thermal expansion properties of BaCo_(0.2)Fe_(0.6)Ti_(0.2)O_(3-δ)

采用修饰的 Pechini方法制备了纯相混合氧离子导体 Ba Co0 .2 Fe0 .6Ti0 .2 O3 -δ(BCFT)样品。 X射线衍射(XRD)证明了该方法制备的陶瓷粉体及烧结样品为单一的六方钙钛矿相结构。扫描电镜 (SEM)观察显示BCFT烧结样品具有均匀的微结构。电导测量显示 :在 5 70℃以下具有电阻负温度系数 (NTC)特征 ,而在 5 70～ 1 0 0 0℃则呈电阻正温度系数 (PTC)特征。结合 BCFT烧结样品的氧非化学计量碘滴定结果分析认为 :高温晶格氧在 5 0 0～ 60 0℃的大量析出使空穴载流子浓度降低是导致电导率出现极值的原因 ,这同时也说明了BCFT在 45 0～ 80 0℃物理热膨胀系数的峰值现象。

BaCo 0.2 Fe 0.6 Ti 0.2 O 3-δ (BCFT) samples were prepared by modified Pechini method. The analysis of XRD demonstrates that the structures of as-synthesized ceramic powders and sintered samples were single hexagonal phase. The observation of SEM shows that the sintered samples are of homogeneous microstructure. The conductivity measurement between 100-1000oC shows that BCFT is a NTC material below 570 ℃, whereas it presents a PTC behavior above 570 ℃. This change is attributed to the hole carrier concentration decreasing with lattice oxygen releasing supported by iodic titration results , which also accounts for the physical thermal expansion coefficient peak behavior of sintered BCFT at 450～800 ℃.