Bridgman growth of lead potassium niobate crystals

Lead potassium niobate Pb2KNb5O15 (PKN) crystals with tetragonal tungsten b ronze (TTB) structure have been grown by the modified Bridgman (BR) method. Nearly sealed Pt crucibles and small temperature gradients in the Bridgman furnace can limit volatilization of PbO and cracking of as-grown PKN cryst als. Transparent PKN crystals of I inch diameter by similar to 2 inch lengt h with brownish color have been grown successfully at a crucible lowering r ate < 0.5 mm/h and a temperature gradient of 10-15 degrees C/cm across the solid-liquid interface. Coupling between twins and growth directions of the crystal is also discussed. (C) 1999 Elsevier Science B.V. All rights reser ved.