IMPROVED GROWTH OF LARGE LEAD-ZINC NIOBATE TITANATE PIEZOELECTRIC SINGLE-CRYSTALS FOR MEDICAL ULTRASONIC TRANSDUCERS

Large piezoelectric single crystals of the Pb[(Zn1/3Nb2/3)(0.91)Ti-0.0 9]O-3 (PZN-PT) binary system have been successfully obtained using a c onventional flux method and a suitable ratio of PZN-PT: PbO flux. The largest crystal had dimensions of 43x42x40 mm and weighed 415g. In ord er to improve growth behavior and reduce the number of nuclei, the tem perature gradient program of the crucible was optimized; that is, the bottom of the crucible was made cooler (>50 degrees C) than the top du ring cooling. A charged composition of 45 mol% PZN-PT and 55 mol% PbO showed good growth results. A large bar-mode electromechanical couplin g factor, k(33)', (84%) for phased array ultrasonic transducers was ob tained. This confirms that large PZN-PT single crystals for phased-arr ay ultrasonic transducers can be grown using a flux method.