Emittance theory for thin film selective emitter

Thin films of high temperature garnet materials such as yttrium aluminum garnet (YAG) doped with rare earths are currently being investigated as selective emitters. This paper presents a radiative transfer analysis of the thin film emitter. From this analysis the emitter efficiency and power density are calculated. Results based on measured extinction coefficients for erbium‐YAG and holmium‐YAG are presented. These results indicate that emitter efficiencies of 50% and power densities of several watts/cm2 are attainable at moderate temperatures (<1750 K).