Dielectric and Piezoelectric Properties of 0.93Pb(Zn1/3Nb2/3)O3–0.07PbTiO3 Piezoelectric Single Crystals for Medical Array Transducers

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Dielectric and piezoelectric properties of 0.93Pb(Zn1/3Nb2/3)O3–0.07PbTiO3 (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, $T_{\text{rt}}$, of PZNT 93/7 SC was 108°C, which is about 40°C higher than that of PZNT 91/9 SC; however, the Curie temperature, $T_{\text{c}}$, of PZNT 93/7 SC was 170°C, which is about 10°C lower than that of PZNT 91/9 SC@. The coupling factor of rectangular bar mode, $k_{33}^{\prime}$, of PZNT 93/7 SC was 84% at room temperature, which is as large as that of PZNT 91/9 SC@. The $k_{33}^{\prime}$ value of PZNT 93/7 SC hardly changed up to about 100°C and then decreased gradually towards the Curie temperature, $T_{\text{c}}$. The degradation temperature of the $k_{33}^{\prime}$ value was roughly in agreement with the phase-transition temperature, $T_{\text{rt}}$, 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 0°C to 80°C, although a dielectric hysteresis was observed in PZNT 91/9 SC in the same temperature range. Therefore, the $T_{\text{rt}}$ is thought to be important for guaranteeing a high $k_{33}^{\prime}$ value and minimum dielectric hysteresis. PZNT 93/7 SC with a reduced Ti content had not only a higher $T_{\text{rt}}$ 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.
2002-11-30

Dielectric and Piezoelectric Properties of 0.93Pb(Zn1/3Nb2/3)O3–0.07PbTiO3 Piezoelectric Single Crystals for Medical Array Transducers

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