Abstract
Recent interest in optimizing composition and synthesis conditions of functional crystals, and the further exploration of new possible candidates for tunable solid-state lasers, has led to significant research on compounds in this family MIMIII(MVIO4)2 (MI = alkali metal, MIII = Al, In, Sc, Fe, Bi, lanthanide; MVI = Mo, W). The vibrational modes, structure transformation, and Al coordination of crystalline, glassy, and molten states of KAl(MoO4)2 have been investigated by in-situ high temperature Raman scattering and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, together with first principles density functional simulation of room temperature Raman spectrum. The results showed that, under the present fast quenching conditions, Al is present predominantly in [AlO6] octahedra in both KAl(MoO4)2 glass and melt, with the tetrahedrally coordinated Al being minor at approximately 2.7%. The effect of K+, from ordered arrangement in the crystal to random distribution in the melt, on the local chemical environment of Al, was also revealed. The distribution and quantitative analysis of different Al coordination subspecies are final discussed and found to be dependent on the thermal history of the glass samples.
Highlights
Molybdates and tungstates doped with transition metal or rare earth ions are important compounds that are found to have potential in tunable laser applications [1,2,3]
Voron’ko et al [15,16] pointed out earlier that the [WO4 ]2− group is more likely to be coordinated to rare earth ions than to alkali metal ions in mixed molten tungstates, the coordination chemistry and structural role of trivalent cations in molten MI MIII (MVI O4 )2 double molybdates/tungstates remain unclear, let alone the more complex situation of rare earth ions
The structure and local Al coordination environment of crystalline, amorphous and molten KAl(MoO4 )2, whose composition belongs to the K2 O-Al2 O3 -MoO3 ternary system, were studied using in-situ high temperature Raman and NMR spectroscopies
Summary
Molybdates and tungstates doped with transition metal or rare earth ions are important compounds that are found to have potential in tunable laser applications [1,2,3]. Voron’ko et al [15,16] pointed out earlier that the [WO4 ]2− group is more likely to be coordinated to rare earth ions than to alkali metal ions in mixed molten tungstates, the coordination chemistry and structural role of trivalent cations in molten MI MIII (MVI O4 ) double molybdates/tungstates remain unclear, let alone the more complex situation of rare earth ions To date, no such results have been obtained on the coordination species of trivalent cations in the family of MI MIII (MVI O4 ) in glassy and molten states. The structure and local Al coordination environment of crystalline, amorphous and molten KAl(MoO4 ) , whose composition belongs to the K2 O-Al2 O3 -MoO3 ternary system, were studied using in-situ high temperature Raman and NMR spectroscopies.
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