STRUCTURE AND PIEZOELECTRIC PROPERTIES OF (Bi_0.5Na_0.5)_1-x-y-zBa_x(Bi_0.5Li_0.5)_ySr_zTiO₃ LEAD-FREE CERAMICS

Abstract

Lead-free ( Bi 0.5 Na 0.5 ) 1-x-y-z Ba x ( Bi 0.5 Li 0.5 ) y Sr z TiO 3 ceramics were prepared by an ordinary sintering method and their structure and piezoelectric properties have been studied. X-ray diffraction patterns show that Ba 2+ , Li + and Sr 2+ diffuse into the Bi 0.5 Na 0.5 TiO 3 lattices to form a solid solution with a pure perovskite structure and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases is formed at 0.04 ≤ x ≤ 0.08 and z < 0.06. The content of Li + has no obvious influence on the crystal structure of the ceramics. The ceramics situated within the MPB exhibit a lower coercive field E c and a larger remanent polarization P r . Because of the formation of the MPB, lower E c and larger P r , the ceramics with x = 0.06, y = 0.075 - 0.125 and z = 0-0.02 possess improved piezoelectric properties. The optimum d 33 (235 pC/N ) and k p (36.3%) are reached at x/y/z = 0.06/0.125/0.02 and 0.06/0.075/0.02, respectively. The deformed P–E loop is also observed near or above T d .