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How does hot forging strengthen halide crystals without greatly reducing infrared transmission?

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optical ceramics High-pressure sodium-vapour lamp bulb.

Hot forging strengthens halide crystals by inducing clean grain boundaries and creating large grain sizes within the material.1

While polycrystalline halide materials typically scatter radiation due to their grain boundaries and porosity—making them less effective for infrared transmission than single crystals—the hot-forging process allows the material to resist plastic deformation without significantly reducing its infrared transmission capabilities. This technique provides the necessary structural integrity for applications such as large infrared windows, which single crystals often lack.1