Microstructure, electrical properties and temperature stability in Bi0.5Na0.5Zr0.95Ce0.05O3 modified R–T phase boundary of potassium-sodium niobium lead-free ceramics
Abstract
(1 − x)K0.48Na0.52Nb0.95Sb0.05O3–xBi0.5Na0.5Zr0.95Ce0.05O3 [(1 − x)KNNS–xBNZC] lead-free piezoelectric ceramics, with doping ratio of x ranging from 0 to 0.05, were synthesized by the conventional solid state sintering method. The phase transition behavior, microstructure and piezoelectric properties of (1 − x)KNNS–xBNZC ceramics were systematically investigated using XRD, SEM, and other devices with different doping amounts of BNZC. It was found that the piezoelectric properties of (1 − x)KNNS–xBNZC ceramics were improved obviously by adding the proper doping amount, 0.03 < x < 0.04, due to the coexistence of rhombohedral and tetragonal phases in the ceramics near room temperature. The piezoelectric constant d33 of the ceramics first increased and then decreased when increasing the doping amount. A remarkably strong piezoelectricity was obtained in ceramics with a ∼441 pC N−1 peak d33 value. The excellent piezoelectric properties of (1 − x)KNNS–xBNZC ceramics with x = 0.034 were obtained: d33 = 441 pC N−1, kp = 0.44, Qm = 31, εr = 2447, tan δ = 0.037, TC = 215 °C, Pr = 15.7 μC cm−2 and EC = 8.2 kV cm−1. With the annealing temperature reaching 250 °C, the d33 values of the ceramics were still greater than 330 pC N−1, which represents good temperature stability for the piezoelectric property. It is believed that such a material system is a very promising candidate for lead-free piezoelectric ceramics.