A large piezoelectric voltage coefficient in aluminate-sodalite-type improper ferroelectric oxides

Dielectric and piezoelectric properties of aluminate-sodalite-type oxides, (Ca1-xSrx)8[AlO2]12{MoO4}2 ((CS)AM-x) have been investigated in the present study. The variation of dielectric anomalies clarifies the phase diagram of (CS)AM-x over a composition range of x = 0.00 – 0.20 to suggest that a unique phase boundary like the morphotropic phase boundary (MPB) exists between x = 0.05 and 0.10. The piezoelectric voltage coefficient g33 at room temperature has been found to culminate around the phase boundary with the value greater than that for the conventional lead-free perovskite-type ferroelectric oxides. The present result sheds light on the development of eco-friendly piezoelectric-active materials with excellent functionalities.