Growth and characterization of KNbO 3 by vertical Bridgman method

Abstract

Potassium niobate (KNbO 3; KN) was grown from a K 2O-Nb 2O 5 flux using the vertical Bridgman (VB) method. By optimizing a flux composition, soaking temperature, the pulling down rate of crucible, and temperature gradient, we were able to successfully grow a pale white and partially colorless KN crystal, 10 mm in diameter and 50 mm in length, without a seed crystal. Blue coloration occurred when the soaking temperature was too high and low soaking temperature resulted in red coloration. The crystal had almost no cracking under optimal temperature conditions and optimal pulling down rate of the crucible. The X-ray pole figures of (0 4 0) and (0 0 4) reflections revealed that the white crystal had a so-called multi-domain structure. It is possible to obtain the high quality KN crystal using VB method.