Investigation of lanthanum substitution effects in yttrium aluminium garnet: importance of solid state NMR and EPR methods

Abstract

In this study yttrium aluminium garnet (YAG) specimens in which yttrium was partially substituted by lanthanum Y3-xLaxAl5O12 (YLaAG) were prepared by an aqueous sol-gel method. The resulting sol was concentrated by slow solvent evaporation at 65 oC. The obtained gels were dried in an oven at 120 oC for 24 h. The obtained precursor gel powders were calcined at 800 oC and 1000 oC in air. YLaAG samples were analyzed by X-ray diffraction (XRD), solid state nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and electron paramagnetic resonance (EPR) methods. Luminescence measurements of YLaAG samples were also recorded. The XRD analysis results showed that only low substitution of yttrium by lanthanum is possible in Y3-xLaxAl5O12 without destroying garnet crystal structure. It was also demonstrated in this study, that solid state NMR and EPR methods are indispensable tools for the explanation of processes and properties observed in the newly synthesized Y3-xLaxAl5O12 compounds.

Influence of different diffusion rates of reaction reagents on the synthesis of yttrium aluminium garnet (YAG)

“…The explicit formulas expressing dependences of the half-time t 1∕2 of YAG synthesis on the average diffusion rate were obtained. In the case of the synthesis by sol-gel reaction method, the half-time could be expressed as t 1∕2 = 5.169 − 2.065e5 ⋅ D(t) + 7.53e9 ⋅ D(t) 2 , when the diffusion rate D t, x, C 3 (t, x) is calculated by (7) and when the diffusion rate D t, x, C 3 (t, x) was calculated by (8) the half-time could be expressed as 4 . In the case of the synthesis by solid-state reaction method, the dependencies are t 1∕2 = 6.69 − 7288e4 ⋅ D(t) + 7.297e6 ⋅ D(t) 2 − 2.918e9 ⋅ D(t) 3 for (7) and t 1∕2 = 10.32 − 3.312e4 ⋅ D(t) + 7.636e7 ⋅ D(t) 2 − 8.4e10 ⋅ D(t) 3 + 3.506e13 ⋅ D(t) 4 for (8).…”

“…Yttrium aluminium garnet (Y 3 Al 5 O 12 , YAG) is an important solid-state laser material known for its high temperature chemical and mechanical stability and widely used in luminescence systems, window materials for a variety of light sources, and fibre-optic telecommunication systems [1][2][3]. Doping with other rare-earth ions, such as Ce 3+ , Nd 3+ , etc., into YAG makes it an ideal material for phosphors and solid-state lasers, which have attracted both technological and industrial interest [4][5][6].…”