Dielectric and piezoelectric properties of 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 piezoelectric single crystals for medical array transducers

Dielectric and piezoelectric properties of 0.93Pb(Zn1/3Nb2/3)O-3-0.07PbTiO(3) (PZNT 93/7) piezoelectric single crystals (PSC) have been investigated. The PZNT 93/7 single crystals (SC) with diameters of 40 mm were grown successfully by the Bridgman method with PbO flux. The dielectric constant of PZNT 93/7 SC at room temperature was about 3500, which is slightly larger than that of PZNT 91/9 SC. Phase-transition temperature, T-rt, of PZNT 93/7 SC was 108degreesC, which is about 40degreesC higher than that of PZNT 91/9 SC; however, the Curie temperature, T-c, of PZNT 93/7 SC was 170degreesC, which is about 10degreesC lower than that of PZNT 91/9 SC. The coupling factor of rectangular bar mode, k'(33), of PZNT 93/7SC was 84% at room temperature, which is as large as that of PZNT 91/9 SC. The k'(33) value of PZNT 93/7 SC hardly changed up to about 100degreesC and then decreased gradually towards the Curie temperature, T-c. The degradation temperature of the k'(33) value was roughly in agreement with the 3 phase-transition temperature, T-rt, from the rhombohedral, to tetragonal phase, measured using the poled PZNT SC. Moreover, no dielectric hysteresis was observed in PZNT 93/7 SC in the temperature range from 0degreesC to 80degreesC, although a dielectric hysteresis was observed in PZNT 91/9 SC in the same temperature range. Therefore, the T, is thought to be important for guaranteeing a high k'(33) value and minimum dielectric hysteresis. PZNT 93/7 SC with a reduced Ti content had not only a higher T-c but also its piezoelectric properties were as good as those of PZNT 91/9 SC near the morphotropic phase boundary (MPB). Therefore, PZNT 93/7 SC achieves the optimum balance of piezoelectric properties and their thermal stability for certain applications performed at Comparatively high temperatures. [DOI:10.1143/JJAP.41.7084].