Control of Near-infrared Spectral Emittance of Polycrystalline Ceramics by Glaze-based Rare-earth Oxide Film Coating

Abstract

本研究では，アルミナ表面に石灰釉をベースとする Er 酸化物膜をコーティングし，膜の組成と 1000℃における近赤外放射率との関係を調べた．その結果，Er 2 O 3 の割合が 50wt%の場合にバルクの 石灰釉中に含まれる Er 量が最大となり，Er の放射ピークである 1.55m における放射率が最大（0.75） となることが明らかとなった． この時， 波長 1～2m におけるふく射エネルギーはアルミナ板時の 1.4 倍である．この膜は多孔質体へのコーティングも可能と考えられるため，実用性に優れた波長選択エ ミッターへの応用に有効である． Normal spectral emittance of alumina plates coated with a lime glaze-based Er oxide film was measured at the temperature of 1000 ℃. As a result, it was revealed that the emittance in the wavelength of 1.55 m, which was the highest peak of emittance of Er, approached to almost the maximum value when compound ratio of Er 2 O 3 to a total pigment was 50 wt%. This is because the lime glaze (bulk amorphous film) can contain the maximum amount of Er in the component. Then, in the wavelength from 1 to 2 m, radiant energy emitted from an alumina plate with the optimized Er oxide film becomes as 1.4 times as that from the substrate only. Since the film can be coated on elements of porous ceramics, the novel coating is assumed to be applicable as selective emitter.[Keywords: spectral emittance, rare-earth oxide, glaze coating, selective emitter]

Thermal radiation properties of porous rare-earth garnet ceramics

“…8),9) Accordingly coating-type selective emitters, which are ceramic coatings on porous substrates and porous coatings on ceramic substrates have been reported. 10)12) Particularly, the Er 2 O 3 porous coating on the alumina ceramic substrate 10) showed relatively high selectivity of approximately 3.3, although its peak emittance was around 0.5.…”