Growth of large and homogeneous PZN-PT single crystals for medical ultrasonic array transducers

Large piezoelectric single crystals of Pb[(Zn_1/3Nb_2/3)_0.91Ti_0.09]O ₃ (PZN-PT 91/9) with high uniformity have been successfully obtained by a novel self-flux method. The best quality crystal had dimensions of 40× 35×30 mm and weighed 330 g. Eight slices of the (100) wafer, which has an area of 25×18 mm without any inclusions of PbO flux or cracks, were obtained. The suppression of inclusions was attributable to deceleration of the growth rate by moderating the amount of raw materials. The suitable selection of the {100} plane to be sliced, i.e, the plane approximately parallel to the nucleation plane, is effective for improving the homogeneity of the wafer. In the 15×20 mm area required for a phased-array transducer, the variations of rectangular bar-mode coupling factor (k ₃₃´) and dielectric constant were within ±5% and ±10% of the average values, respectively. This confirms that large and highly homogeneity PZN-PT 91/9 single crystals for phased-array transducers can be grown using the novel flux method