Investigation of ferroelectric,piezoelectric and mechanically coupled properties of lead-free (Ba 0.85 Ca 0.15 ) (Zr 0.1 Ti 0.9 )O 3 ceramics

Abstract

Lead-free piezoelectric ceramic (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) has been synthesised by solid-state sintering method and the effect of grain size on ferroelectric, piezoelectric, dielectric, mechanical and piezo-electro-mechanical properties was systematically studied. The compacted powders were sintered at three temperatures i.e. 1450°°C, 1500°C and 1550°C for an optimised duration of 5 h and they have exhibited well resolved morphotropic phase boundary with an average grain size ranging from 10 to 25 µm. Enhanced piezoelectric charge, d₃₃ ∼ 560 pC/N and voltage, g₃₃ ∼ 14.3 mV m/N coefficients were obtained for the 1450°C sintered BCZT sample. A maximum strain of around ∼0.14% was obtained which is comparable to that of lead-based piezoelectrics. Variation of relative permittivity with temperature revealed that the curves are independent of frequency, indicating the typical relaxor ferroelectric nature of the samples. A systematic study on cyclic loading was performed to evaluate piezo-electro-mechanical coefficients at different loads which showed hysteresis behaviour. High value of elastic modulus (E) and hardness (H) i.e. 262.7 ± 38.1 GPa and 13.7 ± 1.7 GPa were exhibited by samples sintered at 1450°C, which is higher than that of BCZT synthesised by wet-chemical methods. The results are discussed.