Theoretical modeling of synergistic effect of pores and grains on transmittance in transparent piezoelectric ceramics

Abstract: Transparent piezoelectric ceramics (TPCs) have great application potential in electro-optical-mechanical multi-functional devices. Preparing high-performance TPCs, especially improving the transparency through microstructure regulation, has recently caused extensive discussion. However, there is still controversy about the influence of grains and pores on the transmittance of ceramics, and there is arbitrariness in the estimation of the theoretical transmittance limit. In this paper, taking PMN-PT-based ceramics as an example, theoretical mechanisms for the transmittance are discussed. An inhomogeneous reflection model is derived to improve the theoretical limit of transmittance. The effects of pores and grains scattering on transmittance are investigated. Rayleigh and RGD approximation are discussed to reveal the underlying scattering mechanisms. It is found that Rayleigh approximation is suitable for describing pore scattering, while RGD approximation is suitable for grain scattering. Thus, a Rayleigh-RGD combined model is proposed to describe light scattering in TPCs and successfully employed to fit experimentally measured transmittance curves.