How do grain boundaries reduce infrared transmission through halide ceramics?

In polycrystalline halide ceramics, grain boundaries act as physical discontinuities that scatter radiation, which reduces their infrared transmission.1

While these materials are valued for their ability to transmit infrared light, their polycrystalline nature introduces grain boundaries and porosity that interfere with light propagation. To mitigate these effects and improve performance, manufacturers often use techniques such as hot-forging or fusion-casting to produce large-grained materials or to induce cleaner grain boundaries. These processes help minimize the scattering effect of the boundaries, allowing the ceramic to maintain better optical clarity while retaining the structural strength necessary to resist deformation.1