Optical absorption and selective thermal emission in directionally solidified Al2O3-Er3Al5O12 and Al2O3-Er3Al5O12-ZrO2 eutectics

Al2O3-Er3Al5O12 and Al2O3-Er3Al5O12-ZrO2 eutectic ceramic rods were directionally solidified using the laser floating zone technique at several growth rates. Binary eutectic microstructure consisted in a three-dimensional interpenetrated network of the eutectic phases whereas the ternary eutectic showed a geometrical microstructure at low growth rates and a nanofibrillar pattern at high rates. The microstructure size was strongly dependent on the growth rate, decreasing when the processing rate increased. The optical absorption was measured in the samples at room temperature and Judd–Ofelt analysis was used to model the optical absorption of the Er3+ ions. Thermal emission of the eutectic rods was studied at temperatures up to 1600 °C. An intense narrow emission band at 1.55 μm matching with the sensitive region of the GaSb photoconverter was obtained. The intensity of the selective emission band is larger for the binary eutectic than for the ternary compound and increases as the microstructural size decreases.