Vibrational properties of mixed ( Y 3 Al 5 O 12 ) x - ( Y 3 Sc 2 Ga 3 O 12 ) 1 − x crystals

The vibrational properties of yttrium aluminum garnet (YAG), yttrium scandium gallium garnet (YSGG), and mixed ( YAG ) x - ( YSGG ) 1 − x structures ( 0 < x < 1 ) were investigated by means of Raman spectroscopy. By comparison with the vibrational spectrum of the YAG structure, the attribution of the Raman modes of the YSGG is proposed. The spectra were analyzed with a model of isolated polyhedra and the formation of mixed structures was verified. The Raman modes in the mixed structures lie between those of the pure garnets indicating the presence of truly mixed and not separated phases. An analytical model based on the free tetrahedral approximation to study the position of the vibration frequencies as a function of the relative concentration of the garnets is proposed and applied to the study of the A 1 g breathing mode at 785 cm − 1 in the pure YAG structure and downshifted at 752 cm − 1 in the pure YSGG structure. The proposed analysis allows to verify both the quality of the grown crystal and to assess the relative concentration of the garnets.