Mitigation of Thermal Instability for Electrical Properties in CaZrO(3)-Modified (Na, K, Li) NbO(3) Lead-Free Piezoceramics

Lead-free ceramics 0.96(Na(0.52)K(0.48))(0.95)Li(0.05)NbO(3)-0.04CaZrO(3) (NKLN-CZ) are prepared by using the solid-state procedure and two-step synthesis technique. The crystal structure and thermal stability of NKLN-CZ ceramics sintered at 1140–1180 °C are investigated. All the NKLN-CZ ceramics are ABO(3)-type perovskite phases without impure phases. With the increase in sintering temperature, a phase transition occurs in NKLN-CZ ceramics from the orthorhombic (O) phase to the concomitance of O-tetragonal (T) phases. Meanwhile, ceramics become dense because of the presence of liquid phases. In the vicinity of ambient temperature, an O-T phase boundary is obtained above 1160 °C, which triggers the improvement of electrical properties for the samples. The NKLN-CZ ceramics sintered at 1180 °C exhibit optimum electrical performances (d(33) = 180 pC/N, k(p) = 0.31, dS/dE = 299 pm/V, ε(r) = 920.03, tanδ = 0.0452, P(r) = 18 μC/cm(2), T(c) = 384 °C, E(c) = 14 kV/cm). The relaxor behavior of NKLN-CZ ceramics was induced by the introduction of CaZrO3, which may lead to A-site cation disorder and show diffuse phase transition characteristics. Hence, it broadens the temperature range of phase transformation and mitigates thermal instability for piezoelectric properties in NKLN-CZ ceramics. The value of kp for NKLN-CZ ceramics is held at 27.7–31% (variance of k(p) < 9%) in the range from −25 to 125 °C. The results indicate that lead-free ceramics NKLN-CZ is one of the hopeful temperature-stable piezoceramics for practical application in electronic devices.