Effects of CeO_2 doping on the structure and properties of PSN-PZN-PMS-PZT piezoelectric ceramics

Quinary system piezoelectric ceramics PSN-PZN-PMS-PZT were prepared by using a two-step method. The effects of CeO2 doping on piezoelectric and dielectric properties of the system were investigated at morphotropic phase boundary （MPB）. The results reveal that the relative dielectric constant ε33^T｜ε0, the Curie temperature To, the piezoelectric constant d33, the mechanical quality factor Qm, and the electromechanical coupling coefficient Kp are changed with the increase of CeO2 content. On the other hand, the effects of CeO2 doping on the dielectric properties of PSN-PZN-PMS-PZT piezoelectric ceramics at high electric field are consistent with the change at weak electric field. The values of dielectric constant and dielectric loss are enhanced with the increasing of electric field.

First principles study on lattice vibration and electrical properties of layered perovskite Sr_2M_2O_7(M=Nb, Ta)

In this paper, we performed calculations to investigate the dielectric, piezoelectric properties, Born effective charge （BEC）, and spontaneous polarization of Sr2M207, the method used in our study was a well-known density functional theory based on first-principles. The optimized results were in good agreement with previous experiments and calculations. which indicates that our calculated method is reasonable. The research we have done suggested that greater piezoelectric components of Sr2Nb207 were e31 and e33, and the contributions were derived from the A I. By studying the Born effective charge, it could be seen that the valence of ions changed, and the O of Sr2Nb207 were most obviously that caused by the covalent character of ions and the hybridization of O-2p and Nb-4d. The spontaneous polarization of Sr2Nb2O7 in the [001 ] direction is 25 p_C/cm2, while for Sr2Ta2O7, there was no spontaneous polarization in the paraelectric state. Finally, the effect of pressure on the piezoelectric properties were also investigated, the polarization of Sr2Nb2O7 decreased linearly with the increase alter pressure. All our preliminary results throw light on the nature of dielectric, piezoelectric properties, Born effective charge, and spontaneous polarization of Sr2M2OT, it was helpful for experimental research, the development of new materials, and future applications.

Structural and electrical properties of high Curie temperature Aurivillius phase composite ceramics with largely enhanced piezoelectricity

High performance piezoelectric ceramics with high Curie temperatures(TC) are the bottle necks of relevant high temperature devices. In this study, the electrical performance and microstructure of Li and Mn codoped Aurivillius-type composite ceramics with a composition Ca_(0.99-x_Bi_(6.99+x)(Li Mn)_(0.01) Nb Ti_5O_(24)(x = 0–0.8) were systematically investigated. The results indicated that uniform intergrowth structure with a lattice similar to that of the end member CBT could be formed at a low x value(x < 0.4). Phase separation occurred when more A-site Ca^(2+) ions were replaced by Bi^(3+) ions. Nevertheless, all composite samples showed d_(33) values about 2 to 3 times of that of the constituent phase Ca Bi_4Ti_4O_(15) and Bi_3 Ti NbO_9 with still a high depolarization temperature. The performance of the samples was found to be related to the density and larger lattice distortion along the polarization a axis. The results also demonstrated that formation of the compound system was an effective way in improving the performance of Aurivillius-type high TC piezoelectric ceramics.