Effect of doping on the structure, piezoelectric and electrical properties of Aurivillius type Ca_(0.6)(Na_(0.5)Bi_(0.5))_(0.4)Bi_2Nb_2O_9 ceramics

摘要

Aurivillius phase [Ca-0.6(Na0.5Bi0.5)(0.4)](1-x)(LiCe)(x/2)Bi2Nb2O9 (CNBNLC-100x, x=0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) ceramics were prepared by the conventional solid state method. The LiCe substitution induced structural distortion and orthorhombic distortion of CNBNLC-100x ceramics which influenced piezoelectric activities and Curie temperature, respectively. The results implied that the more structural distortion of lattice leads to higher piezoelectricity. CNBNLC-8 ceramics with ultrahigh T-C of 904 degrees C had a high piezoelectric activity of 17.6pC/N, even after annealing at 600 degrees C for 2h, the d(33) value of CNBNLC-8 ceramics still retained 62.5% of its original value. Ce4+ as donor dopant, the dc resistivity of CNBN ceramics increased with the substitution of Ce4+ for Ca2+. At high temperature region, the extrinsic conductivity changes of the ceramics from p-type to n-type with the increase of Ce4+ doping amount. Further investigation demonstrated that the ac conductive process of ceramics referred to three different mechanisms. The main conduction mechanisms were considered as first-order ionization of oxygen vacancies, second- order ionization of oxygen vacancies and intrinsic dc conductivity at three temperature regions, respectively. All these good electrical properties provided the LiCe doped CNBN ceramics with a large potentiality for high-temperature piezoelectric applications.