Significant increase of Curie temperature and large piezoelectric coefficient in Ba(Ti_0.80Zr_0.20)O₃-0.5(Ba_0.70Ca_0.30)TiO₃ nanofibers

Ba(Ti_0.80Zr_0.20)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ (abbreviated as BTZ-0.5BCT) is a piezoelectric ceramic with a high piezoelectric coefficient d₃₃ (∼620 pC N^-1) and has been regarded as one of the most promising candidates to replace PZT-based materials (200-710 pC N^-1). However, its Curie temperature T_C is relatively low (93°C) limiting its application. In this letter, we found a temperature dependent Raman spectrum in BTZ-0.5BCT nanofibers (NFs), demonstrating a diffused tetragonal-to-cubic phase transition at 300°C. This means that the T_C of the NFs is nearly 207°C higher than that of the normal bulk material. The increased T_C is considered to be associated with the size effect of BTZ-0.5BCT nanoceramic subunits and the nanoporous nature of the fiber, resulting in discontinuous physical properties. The variation of the ferro/piezoelectricity over the fiber surface is attributed to the polycrystalline structure. The d₃₃ (173.32pm V^-1) is improved in terms of the decreased Q factor result in an increase in d₃₃ of 236.54pm V^-1 after polarization. With a high T_C and a very large d₃₃, BTZ-0.5BCT NFs are capable of providing electromechanical behavior used in moderate temperatures.