使用铝电极的BaPbO_3陶瓷的PTCR效应

PTCR Effect of BaPbO_3 Ceramic with Al Electrode

为了研究开发具有低电阻率和正电阻温度系数 (PTCR)的高居里点陶瓷材料 ,以BaCO3和PbO为原料制备了一组La掺杂的陶瓷材料 .实验发现 ,烧结的陶瓷样品在室温下具有极低的电阻率 ,且呈现出和金属导体一样的电导体特征 ;使用铝电极的BaPbO3基陶瓷体表现出PTCR特性 ,并且这种特性可以通过调整掺杂物的量进行改善 .利用扫描电子显微镜和透射电子显微镜对陶瓷的微观结构进行了表征 .微观结构分析表明 ,一薄层的烧结陶瓷表层为具有金属性质的正交结构BaPbO3纳米相 ,并由此使其表现出极低的电阻率 ;具有PTCR特性的陶瓷体内部是由具有畴结构的铁电相组成 ,所以除去烧结陶瓷表层后 ,喷镀铝电极的陶瓷体表现出正电阻温度效应 .

A series of La-doped ceramics was prepared with the materials of BaCO 3-PbO powders in order to obtain the ceramics with high Curie point,low electrical resistivity and PTCR(Positive Temperature Coefficient of Resistivity).It is found from experiments that as-sintered ceramics are of very low electrical resistivities and show the same conductor feature as metal conductors,that the BaPbO 3-based ceramic body with Al electrode displays the PTCR characteristic which can be improved by adjusting the La content.Microstructures of the ceramics were then analyzed by using scanning electron microscopy and transmission electron microscopy.The analytical results reveal that the low resistivity of the ceramic surface layer results from the nanosized BaPbO 3 orthorhombic phase which is of metallic properties,and that the ceramic interior is composed of the ferroelectric phase with domain structures,thus causing the PTCR effect in the ceramic body with Al electrode when the surface layer is removed.