LAUSR

Abstract Selective emitters for thermophotovoltaic systems consisting of directionally solidified Al 2 O 3 -ME 3 Al 5 O 12 (ME: Y, Er and Yb) eutectic coatings on Al 2 O 3 substrates were produced and characterizated. Coatings were deposited by dip-coating on cylindrical substrates. After sintering, a continuous-wave CO 2 laser was used to produce the surface resolidification. The optimization of the processing parameters yielded dense eutectic coatings with good adhesion to the substrate and with 90–200 µm in thickness. All coatings were free of voids and showed a eutectic microstructure consisting of a three dimensional interpenetrated network of Al 2 O 3 and ME 3 Al 5 O 12 . The mechanical properties of the coatings (hardness and fracture toughness) were evaluated by indentation techniques. Thermal emission was studied by heating the rods with a CO 2 laser at temperatures between 1000 and 1400 °C. Selective emission was observed in Er 3+ and Yb 3+ based coatings and attributed to the electronic transitions of the rare earth ions. Er 3+ -coatings showed the best emission properties as selective emitters for thermophotovoltaic converters.