Effect of Sintering Time on Strain in Ceramic Composite Consisting of 0.94Bi0.5(Na0.75K0.25)0.5TiO3-0.06BiAlO3 with (Bi0.5Na0.5)TiO3

The ferroelectric and electric field-induced strain properties of a ceramic composite comprising relaxor 0.94Bi(0.5)(Na0.75K0.25)(0.5)TiO3-0.06BiAlO(3) (94BNKT-6BA) phase and ferroelectric (Bi0.5Na0.5)TiO3 (BNT) phase were investigated as a function of sintering time ranging 4 to 48 h at 1150 degrees C. Large strains were observed with an increase in the sintering time up to 36 h. The 36-h-sintered 94BNKT-6BA+BNT composite exhibited a large piezoelectric strain of 0.372% (4 kV/mm) and a high dynamic d(33)* of 930 pm/V as compared with conventional Pb(Zr, Ti)O-3 (PZT) and other lead-free ceramics. With further sintering up to 48 h, the strain was decreased. The changes in the strain and the ferroelectric properties are thus attributed to the enlargement of ferroelectric grains and the variation of grain's compositions. At sintering times below 36 h, the enlarged ferroelectric grains caused a low field-induced phase transition in the relaxor matrix. At sintering time longer than 36 h, the low strain behavior occurred due to the composition variations in ferroelectric and relaxor grains resulting in diffusion of K and Al elements. (C) 2013 The Japan Society of Applied Physics