Processing, microstructure and optical properties of the directionally solidified Al2O3–EuAlO3 eutectic rods

Al2O3–EuAlO3 eutectic rods were directionally solidified using the Laser-Heated Floating Zone method, also known as Laser-Heated Pedestal Growth technique, with growth rates ranging between 25 and 750 mm/h. The microstructure was found to be highly dependent on the processing parameters, the size of the phases decreasing with the growth rate down 200 nm in samples grown at 750 mm/h. At low rates, an interpenetrated network of the eutectic phases was obtained whereas at high growth rates a tendency towards a nanofibrous pattern was observed. The optical absorption and photoluminescence of the eutectics grown at 100 mm/h and 350 mm/h were measured at room temperature. The Judd-Ofelt parameters, Ω2, Ω4 and Ω6, were obtained from the absorption spectra. Under a 396 nm lamp excitation, a red light emission centred in 616 nm corresponding to the Eu3+ ion was detected. The Eu3+ emission was stronger in the samples with the finer microstructure.

► Directional solidification of Al2O3–EuAlO3 eutectic ceramics using laser floating zone method.
► Microstructure control, phase size and morphology, with processing parameters.
► Change of interpenetrated to fibrillar microstructure with increasing growth rate.
► Optical properties (absorption and luminescence) of Eu3+ studied in the eutectic.
► Red emission from the Eu3+ in samples with fine microstructure.