Large pyroelectric properties at reduced depolarization temperature in A-site nonstoichiometry composition of lead-free 0.94Na x Bi y TiO3-0.06Ba z TiO3 ceramics

Nonstoichiometry lead-free 0.94Na (x) Bi (y) TiO3-0.06Ba (z) TiO3 (N (x) B (y) T-0.06B (z) T) (from x = y = 0.5, z = 1.00 to x = 0.5, y = 0.534, z = 1.02) ceramic compositions were prepared by a conventional solid-state route. XRD shows that the compositions are at a morphotropic phase boundary where rhombohedral and tetragonal phases coexist. The depolarization temperature (T (d)) can be lowered by modifying x, y and z. The pyroelectric coefficient (p) of nonstoichiometry N (x) B (y) T-0.06B (z) T compositions is greatly increased, compared with stoichiometry NBT-0.06BT composition, from 3.15 x 10(-4) C m(-2) A degrees C-1 at room temperature (RT) and 23.9 x 10(-4) C m(-2) A degrees C-1 at T (d), and reaches maxima of 6.99 x 10(-4) C m(-2) A degrees C-1 at RT and 75.3 x 10(-4) C m(-2) A degrees C-1 at T (d) for x = y = 0.52 and z = 1. The figures of merits, F (i), F (v), and F (D), also have been improved from 1.12 x 10(-10) m v(-1) and 0.021 m(2) C-1 to 2.50 x 10(-10) m v(-1), 0.047 m(2) C-1 and 16.63 x 10(-6) Pa-1/2, respectively, for N0.52B0.52T-0.06BT composition at RT. Furthermore, N0.52B0.52T-0.06BT composition shows a huge enhancement in F (i), F (v) and F (D) to 26.9 x 10(-10) m v(-1), 0.39 x 10(-10) m(2) C-1 and 138.7 x 10(-6) Pa-1/2, respectively, at T (d). The same composition also presents F (C) values which are similar to 2.58 and similar to 2.86 (x10(-9) C cm(-2) A degrees C-1) at RT at 100 and 1000 (Hz). N0.5B0.534T-0.06BT and N0.5B0.534T-0.06B(1.02)T compositions show a large p values at a wide temperature range. The enhanced pyroelectric properties make nonstoichiometry N0.52B0.52T-0.06BT composition a promising candidate for pyroelectric and other applications at wide temperatures range.