Bridgman growth of lead potassium niobate crystals

摘要

Lead potassium niobate Pb_2KNb_5O_15 (PKN) crysals with tetragonal tungsten bronze (TTB) sructure have been grown by the modified Bridgman (BR) method. Nearly sealed Pt crucibles and small temeprture gradients in the Bridgman furnace can limit volatilization of PbO and cracking of as-grown PKN crsyals. Transparent PKN crystals of 1 inch diameter by ～2 inch lenth with brownish color have been grown successfully at a crucible lowering rate <0.5 mm/h and a temeprature gradeitn of 10-15 deg C/cm across the solid-liquid interfacfe. Coupling between twins and growth directiosn of the crystal is also discussed.