Growth and ferroelectric properties of tungsten bronze Ba 2− xSr xK 1− yNa yNb 5O 15 (BSKNN) single crystals

Abstract

The undoped and Ce-doped ferroelectric tungsten bronze crystals, specifically Ba 1.5Sr 0.5K 0.75Na 0.25Nb 5O 15 (BSKNN-1) and Ba 0.5Sr 1.5K 0.5Na 0.5Nb 5O 15 (BSKNN-2), have been grown in optical quality using the Czochralski technique. Although both of these crystals are tetragonal with point group 4mm, their growth habit along the [001] direction differs: BSKNN-1 crystals grow in a square shape with four well-defined facets, while BSKNN-2 crystals have an octahedral growth habit with eight well-defined facets. The longitudinal dielectric (ϵ 11) and linear electro-optic ( r 51) constants show strong enhancement when expanding from BSKNN-1 and BSKNN-2 crystals, indicating that the latter could be of major interest for electro-optic, photorefractive and pyroelectric applications.