PbO和Nb2O5共掺杂对CaCu3Ti4O12陶瓷介电性能的影响

Effect of PbO and Nb2O5 co-doping on dielectric properties of CaCu3Ti4O12 ceramics

采用固相反应法制备PbO和Nb2O5共掺杂的CaCu3Ti4O12(CCTO)陶瓷,研究了CCTO巨介电效应机理.通过XRD,SEM,介电频谱及阻抗谱等测试手段,分析纯CCTO陶瓷,PbO掺杂的CCTO陶瓷和PbO、Nb2O5共掺杂CCTO陶瓷的微观结构及介电性能,研究结果表明:掺杂PbO可以显著降低CCTO陶瓷的介电损耗,掺杂摩尔分数2%PbO的CCTO陶瓷的介电损耗从0.13下降到0.03,但其介电常数也显著下降;摩尔分数2%PbO和0.25%Nb2O5共掺杂的CCTO陶瓷,在0.1~1 kHz频率范围内相对介电常数高达4.6×10^4~5.5×10^4,而介电损耗只有0.09左右,且摩尔分数2%PbO和0.5%Nb2O5共掺杂的CCTO陶瓷的相对介电常数在4×10^4左右.因此,PbO和Nb2O5共掺杂可以在增加CCTO陶瓷介电常数的同时降低其介电损耗.结合阻抗谱分析表明,CCTO陶瓷的介电损耗在低频下由晶界电阻决定,在高频下主要受晶粒电容的影响,而介电常数的大小取决于晶粒尺寸和晶界极化,符合IBLC模型.

PbO and Nb2 O5 co-doped CCTO ceramics were prepared by solid state reaction.The mechanism of the giant dielectric effect of CCTO ceramics was studied.The microstructure and dielectric properties of pure CCTO ceramics,PbO doped CCTO ceramics and PbO,Nb2 O5 co-doped CCTO ceramics were analyzed by means of XRD,SEM,dielectric spectrum and impedance spectroscopy.The results show that PbO doping could significantly reduce the dielectric loss of CCTO ceramics.The dielectric loss of CCTO ceramic doped with 2%mole fraction of PbO decreases from 0.13 to 0.03,but its dielectric constant also decreases significantly;2%mole fraction of PbO and 0.25%mole fraction of Nb2 O5 co-doped CCTO ceramic has a high relative dielectric constant of 4.6×10^4-5.5×10^4 in the frequency range of 0.1-1 kHz,and the dielectric loss is only about 0.09.The dielectric constant of 2%mole fraction of PbO and 0.5%mole fraction of Nb2O5 co-doped CCTO ceramic is about 4×10^4.Therefore,the co-doping of PbO and Nb2O5 could reduce the dielectric loss of the CCTO ceramics as well as increase the dielectric constant of them.Combined with the results of impedance spectroscopy,it can be concluded that the dielectric loss of CCTO ceramics is determined by the grain boundary resistance at low frequencies while mainly affected by the grain capacitance at high frequencies.The dielectric constant depends on the grain size and grain boundary polarization of the ceramic,which is consistent with the IBLC model.