Successful aqueous processing of a lead free 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 piezoelectric material composition

Abstract

We report on the successful aqueous processing of a lead free piezoelectric 0.5Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ (BZT–BCT) composition with the final functional properties of the materials unaffected by the various processing steps involved. X-ray diffraction results show a single tetragonal perovskite crystalline phase for the as-received sintered BZT–BCT powder. The purity of the perovskite phase for BZT–BCT powder was found to be controlled even after ageing the material in water for 24 h as a successful surface treatment against hydrolysis. An aqueous suspension of surface treated BZT–BCT powder with 50 vol% solid loading was successfully transformed into micro-sized granules via a freeze granulation (FG) method. Various structural, electrical and mechanical properties of sintered BZT–BCT-FG and BZT–BCT-NG ceramics consolidated from freeze granulated and non-granulated (NG) powders, respectively, were measured. The dielectric constant (ε_r) values of the BZT–BCT-FG sample were found to be higher, with lower dielectric loss (tan δ) values in comparison with those of a sample prepared from the BZT–BCT-NG powder at all temperatures and with all frequency ranges tested. Nanoindentation results revealed that the ability to oppose deformation was nearly 10-fold higher for BZT–BCT-FG (6.93 GPa) than for BZT–BCT-NG ceramics (543 MPa). The functional properties of BZT–BCT-FG samples confirmed the benefits of the aqueous processing approach in comparison with traditional dry pressing.