Growth and Defects Study of A:Al_2O_3(A=Cr,Fe,Ni) Single Crystals

High quality Cr-,Fe-and Ni-doped Al2O3(A:Al2O3) single crystals with a diameter of 6 8 mm and a length of 60 80 mm were successfully produced by the floating zone technique.The relationship between crystal quality and growth conditions was discussed,and the optimum preparation parameter was obtained.The crystals growth direction was determined as 001 by X-ray diffraction.The X-ray rocking curve of the crystal had a FWMH of 0.089o,proving excellent quality of the crystal.The as-grown crystals were characterized by polarized optical microscope and scanning electron microscope,as well as X-ray diffraction.The observed primary crystal defects were sub-angle grain boundaries,inclusions and solute trails.The absorption spectra properties and dielectric constant measurements of A:Al2O3 crystals and fluorescence spectra for Cr:Al2O3 crystals were investigated.In view of the fact that grown A:Al2O3 crystals show good quality,a respectively high dielectric constant er(12.1 15.7),low dielectric loss tanδ(0.0020 0.0002),and favorable thermal stability suggests their utilization as laser matrix,dielectric material for microelectronics and substrate material.