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Phase coexistence and high piezoelectric properties in (K 0.40 Na 0.60 ) 0.96 Li 0.04 Nb 0.80 Ta 0.20 O 3 ceramics

2008; Institute of Physics; Volume: 41; Issue: 3 Linguagem: Inglês

10.1088/0022-3727/41/3/035402

1361-6463

Ling Wu, Jialiang Zhang, Shoufu Shao, Peng Zheng, Chunlei Wang,

Microwave Dielectric Ceramics Synthesis

Lead-free (KxNa1−x)0.96Li0.04 Nb0.80Ta0.20O3 ceramics with x = 0.10–0.70 were prepared by the conventional solid-state reaction technique. The influence of the K/Na ratio on the microstructure, crystallographic structure, phase transition and piezoelectric properties was investigated. It has been disclosed that the phase transition temperature TO–T drastically decreases with x in the narrow compositional range of x = 0.30–0.40 and the phase coexistence of the orthorhombic structure and the tetragonal structure occurs near x = 0.40. The ceramics with x = 0.40 shows high piezoelectric properties (d33 = 254 pC N−1, kp = 51.5%, kt = 49.4% and k33 = 66.6%, respectively) with low dielectric loss (tan δ = 1.5%) and weak temperature dependence between 10 and 85 °C. In particular, the piezoelectric properties remain almost unchanged in the thermal ageing test from −125 to 300 °C. Therefore, this ceramic is considered to be a very promising lead-free piezoelectric material for practical applications. The relation of piezoelectric properties with morphotropic phase boundary and polymorphic phase transition was discussed.