BAO Guocui 1, LI Kun 1, YANG Guang 2, SHI Dongliang 3, LAM Kwokho 3, FANG Bijun 1
(1. School of Materials Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu, China; 2. School of Petrochemical Engineering, Changzhou University, Changzhou 213164, Jiangsu, China; 3. Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, China)
Abstract: Doping with Lanthanides is an important method to improve the piezoelectric property of lead magnesium niobate-lead titanate ceramics. It is difficult to obtain a pure perovskite structure to prepare La-doped lead magnesium niobate-lead titanate (La-PMN-PT) ceramics by the traditional niobate process. However, a pure perovskite structure is a key factor for the piezoelectric property of La-PMN-PT ceramics. In this work, Pb 0.9625 La 0.025 (Mg 1/3 Nb 2/3)1−x TixO3 (x = 0.28–0.31) piezoelectric ceramics were prepared by the two-step calcination process. The effect of Ti content on the electrical properties of the ceramics was studied. It was found that the La-PMN-PT ceramic samples presented a pure perovskite structure, with an average grain size of (4.50±0.23) μm. The crystal structure of the samples gradually transformed from the rhombohedral phase to the tetragonal phase with increasing Ti content. The morphotropic phase boundary (MPB) appeared near the Ti content of 0.30. With this composition, piezoelectric coefficient d33 of 1010 pC·N−1, electromechanical coupling coefficient kp of 0.69, relative dielectric permittivity εr of 10766, and field-induced strain S of 0.23% at 1 Hz, 1.5 kV·mm−1 are achieved. The two-step calcination process could effectively inhibit the generation of the pyrochlore phase and improve the electrical properties of the ceramics.
Key words: piezoelectric ceramics; crystalline structure; piezoelectric property; dielectric property; ferroelectric property