Growth and characterization of ternary BiScO3–Pb(Cd1/3Nb2/3)O3–PbTiO3 ferroelectric single crystals with high Curie temperature

Abstract

Ferroelectric single crystals of a ternary perovskite solid solution, BiScO₃–Pb(Cd_1/3Nb_2/3)O₃–PbTiO₃ (BS–PCN–PT), have been successfully grown by the top-seeded solution growth method for the first time. The crystals with dimensions up to 2.5 × 2.5 × 1 cm³ were obtained. The structure of the BS–PCN–PT crystals has been studied by high-resolution X-ray diffraction, combined with polarized light microscopy, showing a tetragonal symmetry. The grown crystals exhibit a pseudo-cubic morphology with the (001) facets, suggesting a dominant {100}-growth process. Interestingly, a single ferroelastic domain state was found in most (001) platelets cut from the as-grown crystals. The domain structures and characteristics were carefully investigated by a combination of polarized light microscopy and piezoresponse force microscopy. The single-domain crystals possess a high average coercive field (E_c ∼ 30 kV cm⁻¹) and a high remanent polarization (25 μC cm⁻²). An unpoled piezoelectric constant d₃₃ of the single-domain crystal is up to 111 pC N⁻¹ due to its self-polarization. The Curie temperature T_C is found to be 423 °C by means of dielectric measurements, which is much higher than that of relaxor-based Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PMN–PT) piezocrystals. Moreover, the dielectric properties exhibit an excellent thermal stability up to 300 °C. A careful discussion about how the domain state may affect electromechanical properties has been carried out. The high T_C, large coercive electric field, and high remanent polarization of the single-domain BS–PCN–PT crystals make this material a promising candidate for applications in a wider temperature range and at higher power compared to the PMN–PT crystals.