Large piezoelectricity response in Li and Ti (or Zr) co-alloyed w-AlN

Abstract

As one of the most important piezoelectric materials for piezoelectricity related devices, the performance of wurtzite-type aluminum nitride (w-AlN) is still inhibited by its low piezoelectric coefficients. Herein, we have proposed a new co-alloying w-AlN system by Li+ and Ti4+ (or Zr4+) in a ratio of 1:2 and systematically compared its piezoelectric properties with state-of-the-art Sc-alloyed w-AlN via the first-principle method. It is found that the co-alloyed w-AlN shows obvious advantages over Sc-alloyed w-AlN in nearly all aspects of piezoelectric performance. The piezoelectric strain coefficient (d33) of (LiTi2)0.375Al0.625N reaches 213.25 pC/N, about 8 times and 41 times that of Sc0.375Al0.625N and pure w-AlN, respectively. Additionally, the large enhancement of piezoelectricity of co-alloyed w-AlN was successfully related to the elastic softening, the increased Born effective charge (Z∗), and the decreased internal strain sensitivity (dudδ). This work provides a new way to enhance the performance of incumbent piezoelectric materials by accessible elements instead of Sc.