Effect of K content to lead-free SrBi_4Ti_4O_(15)-(Na_(0.5)Bi_(0.5))Bi_4Ti_4O_(15) piezoelectric ceramics

摘要

The high-performance lead-free piezoelectric ceramics based on a mixed bismuth layer-structured ferroelectric Sr_(0.9)((Na_(1-x)K_x)_(0.5)Bi_(0.5))_(0.1)Bi_4Ti_4O_(15) (x = 0.0, 0.12, 0.16, 0.2, 0.24, 0.28, 0.32) (abbreviated as SNKBT) were synthesized by conventional solid-stated processing. The phase structure, microstructural morphology, and electrical properties of SNKBT ceramics with different K content were studied carefully. With the increase of K content, the lattice parameters, a and b (supposing b ＞ a), were found to be almost unchanged, however, the lattice parameters c was found to increase monotonously. Therefore the unit cell volume increased monotonously. The plate-like grain size of SNKBT ceramics was observed to decrease with the increase of K content. The piezoelectric activities of SNKBT ceramics is improved by the modification of K content. The Curie temperature (T_c) and piezoelectric constant (d_(33)) for the 0.24 mol% K-contented SNKBT solid solutions were found to be 569 ℃ and 20 pC/N, respectively. Meanwhile the piezoelectric ceramics possess stable aging performance and thermal annealing properties, which, together with the high T_c and d_(33) demonstrating that the SNKBT materials are promising candidates for high-temperature applications.