Journal of the American Ceramic Society 2018-04-10

Improving piezoelectric properties and temperature stability for KNN‐based ceramics sintered in a reducing atmosphere

Zhenyong Cen; Yichao Zhen; Wei Feng; Peiyao Zhao; Lingling Chen; Chaoqiong Zhu; Xiaohui Wang; Longtu Li

Index: 10.1111/jace.15584

Full Text: HTML

Abstract

Lead‐free 0.955K0.5Na0.5Nb1‐zTazO3‐0.045Bi0.5Na0.5ZrO3+0.4%MnO ceramics (abbreviated as KNNTaz‐0.045BNZ+0.4Mn) were prepared by a conventional solid‐state sintering method in a reducing atmosphere (oxygen partial pressure of 1×10‐10 atm). All ceramics with a pure perovskite structure show the two‐phase coexistence zone composed of rhombohedral and tetragonal phase. Ta5+ ions substitute for Nb5+ ions on the B‐site, which results in a decrease in the R phase fraction in the two‐phase coexistence zone. The R‐T phase transition temperature moves to room temperature due to the substitution of Nb5+ ions by Ta5+ ions. A complex domain structure composed of small nano‐domains (~70 nm) formed inside large submicron domains (~200 nm) exists in KNNTa0.02‐0.045BNZ+0.4Mn ceramics, which can induce a strong dielectric‐diffused behavior and improve the piezoelectric properties. The temperature stability for the reverse piezoelectric constant d*33 for the KNNTaz‐0.045BNZ+0.4Mn ceramics can be improved at z=0.02. Excellent piezoelectric properties (d33 = 328 pC/N, and d*33 = 475 pm/V at Emax = 20 kV/cm) were obtained for the KNNTa0.02‐0.045BNZ+0.4Mn ceramics.