Low temperature dielectric and pyroelectric studies of the morphotropic phase boundary of lead barium niobate (PBN) single crystals

Abstract

Abstract Lead barium niobate (Pb1−xBaxNb2O6, PBN) is one of the oxide octahedron-type ferroelectrics with a tungsten bronze-type structure.1,2,3 The crystal has a prototype symmetry of tetragonal 4/mmm at a temperature higher than Tc. At T<Tc, the crystal possesses either a ferroelectric tetragonal phase 4mm (for 1−x<0.63) with a polarization vector along [001] direction or a ferroelectric orthorhombic phase m2m (for 1−x>0.63) with a polarization vector along the [110] direction (referring to the prototype symmetry).4,5 For a composition in the vicinity of 1−x-0.63, a morphotropic phase boundary exists and separates two ferroelectric phases (tetragonal 4mm and orthorhombic m2m). It is reported when a composition is close to the MPB, many useful physical properties would be enhanced (e.g., dielectric constant6,7, piezoelectric coefficient7, and pyroelectric coefficient8) and are essentially temperature independent. It is thus of theoretical and practical significance to study MPB PBN compositions.