When observing the microstructure of ceramics, researchers frequently see residual pores and structural defects, such as segregation at grain boundaries. These defects serve as scattering sources of incoming light, which affect the optical properties of ceramics and make them inferior to single crystals in optical applications.

But what if these defects are removed? Could ceramics that contain pristine grain boundaries achieve optical properties similar to single crystals without grain boundaries?

Traditionally, the answer to this question is no. In the 19^th century, Lord Rayleigh was awarded the Nobel Prize in Physics for constructing his own scattering theory based on computational science. According to his theory, even if these micrometer- to nanometer-scale defects are removed from the ceramic, scattering from grain boundaries (subnanometer scale) cannot be avoided.