La^(3+)掺杂对CaBi_(2)Nb_(2)O_(9)压电陶瓷结构与电学性能的影响

Influence of La^(3+)Doping on Structure and Electrical Properties of CaBi_(2)Nb_(2)O_(9) Piezoceramics

采用传统固相法制备Ca1-xLaxBi_(2)Nb_(2)O_(9)(CBN-xLa,x=0.00,0.02,0.04,0.06,0.08,0.10)陶瓷,研究了La^(3+)掺杂对CaBi_(2)Nb_(2)O_(9)陶瓷的晶体结构、微观形貌、介电性能、压电及铁电性能以及高温导电机制的影响.结果表明,适量的La^(3+)取代Ca^(2+)优化了晶体结构,细化晶粒,通过施主掺杂降低了氧空位,有效地改善了CaBi_(2)Nb_(2)O_(9)陶瓷的电性能.其中Ca0.92La0.08Bi_(2)Nb_(2)O_(9)是最优组分,获得压电性能d33、Curie温度T_(C)和剩余极化强度2Pr分别为11.7 pC/N、905℃和9.51μC/cm^(2),并且在550℃条件下的tanδ为3.87%,退火处理后,所有组分样品在800℃条件下均保持较稳定压电性能.复阻抗谱表明阻抗是由晶粒晶界共同作用,导电机制与氧空位有密切关系,且La^(3+)能有效提高高温电阻率,使得其在高温传感器中具有应用潜力.

La^(3+)-doped Ca_(1-x)CaBi_(2)Nb_(2)O_(9)(CBN-xLa,x=0.00,0.02,0.04,0.06,0.08,0.10)piezoceramics were synthesized by a solid-state reaction method.The crystal structure,microstructure,dielectric,piezoelectric and ferroelectric properties as well as high-temperature conductive mechanism of La^(3+)-doped CBN ceramics were investigated.The results show that an appropriate amount of La3!donor ion substituted for Ca^(2+)ion can optimize the crystal structure,decrease the grain size,reduce the oxygen vacancy,and effectively improve the electrical properties of CBN ceramics.The Ca_(0.92)La_(0.08)Bi_(2)Nb_(2)O_(9) ceramics with the optimal performance(high piezoelectric coefficient(d_(33)=11.7pC/N)and the Curie temperature(T_(c)=905°C),remanent polarization(2P_(r)=9.51 μC/cm^(2))and low dielectric loss,(tanδ=3.87%at 550℃)).After annealing,the piezoelectric properties of all the samples remain stable at 800℃.According to the complex impedance plots,the grain boundary and grain both contribute the impedance,and the conduction mechanism is closely related to oxygen vacancies.Moreover,La^(3+)-doping can effectively improve the resistivity of CBN ceramics at high temperatures,indicating a potential application in high-temperature sensors.