Structure and temperature effects on Nd3+ spectra in polycrystalline mixed scandium aluminum garnets Y3Sc Al5−O12

Abstract New spectroscopic data obtained from high resolution low temperature absorption and emission spectra of Nd 3+ in mixed scandium aluminum garnets Y 3 Sc x Al 5 − x O 12 – ( x = 0–2) translucent ceramics revealed transition dependent composition effects: modification of the shapes (Lorentz at x = 0 and 2, quasi-Gauss at x = 1, x -dependent asymmetric for other x values, with obvious multicenter structure for low x ), widths and shifts of the lines. Nd 3+ electronic structure dependence on structural changes with composition is analyzed in terms of nephelauxetic effect and maximum splitting of manifolds: Sc 3+ co-doping reduces the nephelauxetic effect, and the increase of 4 F 3/2 splitting from 85 cm −1 ( x = 0) to 98 cm − 1 ( x = 2) denotes the lowering of local symmetry. The multicenter structure and inhomogeneous broadening of Nd 3+ lines is attributed to crystal field distributions determined by the random occupancy of the octahedral sites by Sc 3+ and Al 3+ . For low x (0.2) the resolved two satellites S 1 , S 2 that accompany Nd:YAG lines are correlated to anisotropic crystal field perturbations produced by the n.n. Sc 3+ by analogy to those determined by Y 3+ -antisites (excess of Y 3+ ions that enter in octahedral sites of the melt-grown YAG crystals). The temperature evolution of the Nd 3+ spectral characteristics (line intensity, shift, broadening) in the 10–300 K range is analyzed in terms of thermal population of the Stark levels, of the effect on electron–phonon interaction and on lattice expansion. The relevance of the spectroscopic properties on the laser emission characteristics in these systems is discussed.