Emittance-controlled Ceramic Emitter for a Thermophotovoltaic

Abstract

R₃Al₅O₁₂ (R: rare-earth) ceramics are one of the emitter candidates for thermophotovoltaic (TPV) systems. We conducted a detailed study on the fabrication, the microstructural characterization, and the thermal emissive performance of porous Yb₃Al₅O₁₂ (YbAG) emitters. The emitters were synthesized by solid-state reaction and sintered with various conditions using ball-milling powders, which result in different porosities of the samples. Thermal radiation measurements revealed that the porous ceramics had excellent selectivity regarding emission wavelengths and optimal porosity of sintered bodies for emittance wavelengths selectivity are different according to grain size of powders related to sintered body grain size. Generally, in spite of the narrow-band thermal emissions of rare-earth ions, most ceramics do not present sufficient selectivity because of their transparency in the near infrared range. This paper discusses the mechanism of high selectivity from observations of the microstructures of developed YbAG ceramics.