Thermal stability of the piezoelectric strain constant d₃₁ of AC poled (1 − x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ single crystals

Abstract

Alternating current poled (ACP) (1 − x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ (PMN–xPT) single crystals (SCs) exhibited 8–49 % higher piezoelectric strain constant length extensional mode (d₃₁) at room temperature than direct current poled (DCP) SCs. However, thermal stability of these d₃₁ was 13 to 69 °C lower for ACP SCs than for DCP SCs, indicating lower thermal stability. These results were obtained for four rhombohedral compositions of PMN–xPT SCs (x = 0.26, 0.295, 0.305, and 0.33) prepared by the one-charge Bridgman method. Microstructures observed by scanning electron microscopy showed that the average 109° domain walls width (ADW) gradually increased proportionally with increasing PT from PMN–0.26PT to PMN–0.33PT, with the highest d₃₁ (−1700 pC/N) in the PMN–0.305PT SC. The PMN–0.26PT and PMN–0.33PT SCs showed almost the same piezoelectric properties, but their microstructures, ADW, and thermal stability were clearly different, indicating that ADW is not the only primary factor determining high piezoelectric properties. These experimental results suggest that accurate control of PMN–xPT SC composition, SC growth method, and optimal ACP condition setting are essential to simultaneously satisfy excellent piezoelectric properties and thermal stability after ACP.