Sr和Co共掺杂对PrAlO_3钙钛矿氧化物的结构和电性能的影响

Effect of Strontium and Cobalt Co-doping on the Structural and Electrical Properties of PrAlO_3 Perovskite Oxides

采用柠檬酸盐法结合高温烧结制备T（Pr,Sr）（Al，Co）O3-δ系列钙钛矿氧化物导电陶瓷。使用X射线衍射（XRD）、扫描电镜（SEM）和直流四线法等手段对样品的物相、微观结构和电性能进行了表征。结果表明：所制备的Pn0.9Sr0.1Al1-yCoyO3-δ（y=0．1—0．5）陶瓷均为单相菱方钙钛矿结构．在掺杂范围内其晶胞体积、相对密度和电导率都随Co掺杂量y的增加而增大，但电导率的增幅在逐步减小；所有陶瓷样品在空气中都是氧离子与电子空穴的混合导体，电导行为符合小极化子跳跃机制。对于Pr1-xSrxAl0.5Co0.5O3-δ（x=0．1—0．4）陶瓷．当x=0．2时样品有较明显的第二相（Pr，Sr）CoO3析出，说明Sr在该体系的固溶限在10。20at％之间，而且随着Ⅳ的进一步增加，（Pr,Sr）CoO3增多并成为主相：在测量温度范围内，Pr1-xSrxAl0.5Co0.5O03-δ的电导率随x的增加大体呈现出一个先增大后减小的变化趋势．在x=0.3附近达到一个最大值，当∞〉t0．2时还可观察到明显的半导体一金属性转变，且转变温度随X的增加而逐渐降低。

Novel Sr- and Co-codoped （Pr,Sr） （A1,Co）O3-δ perovskite oxide conducting ceramics were prepared by citrate process combined with subsequent high-temperature sintering. The phase composition, microstructure and electrical properties of the obtained ceramics were characterized by XRD, SEM and direct current four-wire method. The experimental results show that all the as-prepared Pro.gSroaAll-rCoyO3-δ （y=0.1-0.5） ceramics are a single-phase rhombohedral perovskite structure, and their unit cell volumes, relative densities and electrical conduetivities increase with increasing y in the doping range, while the increasing rate in electrical conductivity progressively decrease. Furthermore, these samples are a mixed conductor of oxygen ion and hole in air and their electrical conductivities are absolutely dominated by p-type conduction. The temperature dependence of electrical conductivity for Pr0.gSr0.1All-yCoyO3-δcan be described by the small polaron hopping mechanism. For the as-prepared Prl-xSrxA10.sCo0.503-δ （x=0.1 -0.4） ceramics, a second phase （Pr,Sr）CoO3 obviously precipitates when x=0.2, indicating that the solid solubility limit of Sr on A site in this system is between 10at% and 20at%, and the （Pr, Sr）CoO3 phase in samples increases gradually and finally becomes the main phase with further increase in Sr content. It is found that the electrical conductivity of Prl-xSrxA105Co0503-δ ceramics roughly exhibits a trend of first increase and then decrease with increasing x in the whole examined temperature range, and reaches the maximum value at around x= 0.3. Additionally, the semiconductor-to-metal transition in the conduction behavior is obviously observed for the samples with x ≥ 0.2, and the transition temperature gradually decreases with increasing Sr content.