Diffusion phase transition and dielectric characteristics of Bi0.5Na0.5TiO3–Ba(Hf,Ti)O3 lead-free ceramics

Lead-free ceramics based on bismuth sodium titanate (Bi0.5Na0.5TiO3, BNT)-barium hafnate titanate (Ba(Hf0.05,Ti0.95)O3, BHT5) were prepared by a two-step sintering process. The BNT–BHT5 ceramics sintered at 1180 ∘C for 2 h in air showed a pure perovskite structure. The results show that the phase transition temperature ( T m ) is suppressed dramatically with a small amount of BHT5 content and then decreased gradually with more BHT5 in the compounds. The diffusion of the phase transition is more distinct for the samples around the morphotropic phase boundary (MPB) of BNT–BHT5 system. In the (1−x)BNT–xBHT5 system, high piezoelectric constants were obtained at x = 0.08 , which is a tetragonal phase near the MPB region. The BNT–BHT5 system is expected to be a new and promising candidate for lead-free dielectric and piezoelectric ceramics.