Nondestructive evaluation of large-area PZN-8%PT single crystal wafers for medical ultrasound imaging probe applications

Abstract

A nondestructive quality evaluation and control procedure for large-area, (001)-cut PZN-8%PT wafers is described. The crystals were grown by the flux technique engineered to promote (001) layer growth of the crystals. The wafers were sliced parallel to the (001) layer growth plane. Curie temperature (Tc) variations, measured with matching arrays of dot electrodes (of 5.0 mm in center-to-center spacing), were found to be better than ±4.0°C both within wafers and from wafer to wafer. After selective dicing to give final wafers of narrower Tc distributions (e.g., ±3.0°C or better), the wafers were coated with complete electrodes and poled at room temperature at 0.7-0.9 kV/mm. Typical overall properties of the poled wafers were: K3 T = 5,200 (±10% from wafer to wafer), tan δ < 0.01 (all wafers), and kt = 0.55 (±5%) (all percentage variations are in relative percentages). Then, the distributions of K3 S, tan δ, and kt were measured by the array dot electrode technique. The variations in K3 S (hence K3 T) and kt within individual wafers were found to be within ±10% and ±5%, respectively. The dielectric loss values, measured at 1 kHz, were consistently low, being