CHEN Zilong, JIANG Xiangping, CHEN Chao, HUANG Xiaokun, JIANG Yujian
(Jingdezhen Ceramic Institute, Jingdezhen 333403, Jiangxi, China)
Abstract: Bismuth layered ceramics, (Na0.5Bi0.5)1-xLaxBi2Nb2O9 (NBN-xLa3+, x = 0.00, 0.04, 0.08, 0.16, 0.24, 0.32, 0.40), were prepared by using the conventional solid-state reaction method. The effect of La3+ on phase structure, microstructure and electrical properties of the Na0.5Bi2.5Nb2O9 ceramics were studied. XRD and Raman results indicate that La3+ has been incorporated into the lattice of NBN and the degree of orthorhombic distortion was reduced. The structural distortion and the reduction of oxygen vacancy concentration induced by the doping of La3+ made the ceramics to be more easily polarized, so that the piezoelectric activity was improved. The sample with x = 0.24 exhibits the optimal electrical properties, with Tc = 647 ℃, εr = 328, tanδ = 1.09%, d33 = 22.8 pC/N, Qm = 3259. It also possesses excellent temperature stability at high temperatures. The piezoelectric constant d33 remains to be 20.3 pC/N after annealing at 500 ℃ for 2 h, which is 89% of the initial value.
Key words: bismuth layered ceramics; structural distortion; oxygen vacancy concentration; temperature stability