Bi_0.5Na_0.5TiO₃-BaTiO₃无铅压电陶瓷的微观结构和电学性能研究

Microstructure and Electrical Properties of Bi_0.5Na_0.5TiO₃-BaTiO₃ Lead-Free Piezoelectric Ceramics

摘要: 本实验采用固相反应法制备Ba_0.5Na_0.5TiO₃-xBaTiO₃ (BNT-xBT, x = 0、0.04、0.05、0.06、0.07、0.08)压电陶瓷，系统研究BT含量对陶瓷相结构、微观形貌、及电学性能的影响。结果表明：均含有三方相和四方相，适量BT掺杂可显著细化晶粒、提升致密度，在x = 0.06时获得最小平均晶粒尺寸(D_λ = 1.26 μm)。陶瓷处于准同型相界处(MPB)，为三方相和四方相共存态，MPB组分(x = 0.06)表现出最优的综合性能：其压电常数d₃₃约为180 pC/N，平面机电耦合系数k_p为0.336，剩余极化强度P_r最高(44.12 μC/cm²)，矫顽场E_c最低(34.29 kV/cm)，这主要源于MPB区域的结构失稳性大幅增强了畴翻转响应及极化能力。然而，介电温谱与变温压电测试同时揭示，BT掺杂在提升室温压电活性的同时，亦显著增强了材料的弛豫特性，导致介电峰宽化、特征温度T_m降低，且退极化温度T_d明显下降，从而制约了其高温应用中的热稳定性。

Abstract: A series of piezoelectric ceramics Ba_0.5Na_0.5TiO₃-xBaTiO₃ (BNT-xBT, x = 0, 0.04, 0.05, 0.06, 0.07, 0.08) were prepared via the solid-state reaction method. The effects of BT content on the crystal structure, microstructure, and electrical properties of the ceramics were systematically investigated. Results indicate that at the quasi-isotropic phase boundary, where trigonal and tetragonal phases coexist, appropriate BT doping significantly refines grain size and enhances density, yielding the smallest average grain size (1.26 μm) at x = 0.06. Electrical property testing revealed that the MPB composition (x = 0.06) exhibited optimal comprehensive performance: its piezoelectric constant d₃₃ was approximately 180 pC/N, the plane electromechanical coupling coefficient k_p was 0.336, highest residual polarization intensity P_r (44.12 μC/cm²), and lowest coercive field E_c (34.29 kV/cm). This stems primarily from the significantly enhanced domain reversal response and polarization capability due to structural instability in the MPB region. However, both dielectric temperature-dependent measurements and variable-temperature piezoelectric testing reveal that while BT doping enhances room-temperature piezoelectric activity, it also markedly increases the material’s relaxation characteristics. This leads to broadened dielectric peaks, reduced characteristic temperature T_m, and a significant decrease in depolarization temperature, thereby limiting thermal stability in high-temperature applications.