Structure and properties of novel antiferroelectric PbHfO3-Pb(Mg1/2W1/2)O3 single crystals grown from high-temperature solution

Abstract

Antiferroelectric (AFE) materials with perovskite structure have attracted great interest due to their distinctive structural complexity and useful physical properties. So far, most studies have focused on polycrystalline materials. Compared with the preparation of ceramics and films, the growth of Pb-based AFE single crystals with high quality is a more challenging task because of the high melting point, incongruently melting and the volatilization of Pb-containing components at high temperatures. In order to develop new antiferroelectric materials for energy storage applications and understanding the mechanisms of phase transitions and domain structure, single crystals of a new AFE-AFE solid solution of PbHfO3-Pb(Mg1/2W1/2)O3 (PHf-PMW) were successfully grown for the first time by the high-temperature solution growth method using the mixtures of PbO-B2O3 and Pb3O4-B2O3 as complex flux, respectively, and the grown crystals were characterized in terms of their crystal structure, dielectric properties and domain structure. It was found that Pb3O4 as the main flux component is more favorable than PbO as it lowers the melting point of the system and provides a more stable growth, leading to PHf-PMW crystals of larger size, better quality, higher optical transparency and less defects or inclusions. The structural analysis by XRD shows an orthorhombic Pbam symmetry at room temperature for the grown crystals, which is of antiferroelectric nature. By comparing the sequence and temperature of the phase transitions to the PHf-PMW ceramics, the compositions of the grown crystals are estimated to be 0.99PHf-0.01PMW and 0.985PHf-0.015PMW, respectively. Compositional segregation is observed in the grown crystals, which can be attributed to the incongruently melting character on the one hand, and the differences in the ionic radius and electronegativity of the oxygen anion and various B-site cations in the crystal lattice on the other hand. The observation and analysis of the ferroic domains by polarized light microscopy based on optical crystallography reveal domain structures consisting of two sets of domains with extinction directions parallel to the 〈110〉cub direction, confirming the orthorhombic symmetry. This work provides new experimental strategies in growing the high-quality antiferroelectric crystals of complex perovskite structure and a better understanding of their structure and properties for both fundamental studies and potential applications in optoelectronics and energy storage.