Garnet infrared windows

Abstract The infrared (IR) transparency of garnets and cubic antimonates, with a structure similar to garnet, were determined by density functional theory (DFT) calculations. The maximum frequency at the Brillouin zone center was scaled by a factor of 2 to determine IR cutoff. DFT calculations for bulk modulus and bandgap were also done. The calculations were compared with transparency determined from digitized Fourier‐transform infrared (FTIR) spectra for powder and for bulk specimens. Trends for predictions from DFT calculations agree with those determined from FTIR and bulk spectra. Measurements of IR transmittance from room temperature to 1500°C were made for polycrystalline Y 3 Al 5 O 12 (YAG) and single‐crystal Gd 3 Ga 5 O 12 (GGG) garnet. Optical, structural, thermodynamic, and thermophysical properties from literature data were collected for a variety of garnet compositions, and where possible, compared with DFT calculations. Garnets with the best combinations of properties for windows are discussed.