Effects of lattice parameters on piezoelectric constants in wurtzite materials: A theoretical study using first-principles and statistical-learning methods

Longitudinal piezoelectric constant (e(33)) values of wurtzite materials, which are listed in a structure database, are calculated and analyzed by using first-principles and statistical learning methods. It is theoretically shown that wurtzite materials with high e(33) generally have small lattice constant ratios (c/a) almost independent of constituent elements, and approximately expressed as e(33) proportional to c/a - (c/a)(0) with ideal lattice constant ratio (c/a)(0). This relation also holds for highly-piezoelectric ternary materials such as ScxAl1-xN. We conducted a search for high-piezoelectric wurtzite materials by identifying materials with smaller c/a values. It is proposed that the piezoelectricity of ZnO can be significantly enhanced by substitutions of Zn with Ca. (C) 2018 The Japan Society of Applied Physics.