Piezoelectric properties in (K0.5Bi0.5)TiO 3-(Na0.5Bi0.5)TiO3-BaTiO 3 lead-free ceramics

Lead-free piezoelectric ceramics with compositions around the morphotropic phase boundary (MPB) x(Na
_0.5
Bi
_0.5
)TiO
_3-y
(K
_0.5
Bi
_0.5
)TiO
₃
-zBaTiO
₃
[x + y + z = 1; y:z = 2:1] were synthesized using conventional, solid-state processing. Dielectric maximum temperatures of 280degC and 262degC were found for tetragonal 0.79(Na
_0.5
Bi
_0.5
)TiO
₃
-0.14(K
_0.5
Bi
_0.5
)TiO
₃
-0.07BaTiO$ d3 (BNBK79) and MPB composition 0.88(Na
_0.5
Bi
_0.5
)TiO
₃
-0.08(K
_0.5
Bi
_0.5
)TiO
₃
-0.04BaTiO$ d3 (BNBK88), with depolarization temperatures of 224degC and 162degC, respectively. Piezoelectric coefficients d
₃₃
were found to be 135 pC/N and 170 pC/N for BNBK79 and BNBK88, and the piezoelectric d
₃₁
was determined to be -37 pC/N and -51 pC/N, demonstrating strong anisotropy. Coercive field values were found to be 37 kV/cm and 29 kV/cm for BNBK79 and BNBK88, respectively. The remanent polarization of BNBK88 (~40 muC/cm
²
) was larger than that of BNBK79 (~29 muC/cm
²
). The piezoelectric, electromechanical, and high-field strain behaviors also were studied as a function of temperature and discussed