Gadolinium Aluminate Garnet ( Gd3Al5O12): Crystal Structure Stabilization via Lutetium Doping and Properties of the ( Gd1− x Lu x)3 Al5O12 Solid Solutions ( x = 0-0.5)

To suppress the thermal decomposition and stabilize the crystal structure of Gd₃Al₅O₁₂ ( GdAG) garnet, GdAG was doped with significantly smaller Lu³⁺ to form (Gd,Lu)AG solid solutions. The precursors for ( Gd_{1− x} Lu _x)₃ AG ( x = 0-0.5), with a general formula of ( NH₄) _x Ln₃Al₅(OH) _y( CO₃) _z· n H₂O ( Ln = Gd and Lu), were synthesized via carbonate co-precipitation from the mixed solutions of aluminum, lutetium, and gadolinium nitrates using ammonium hydrogen carbonate as the precipitant. The results showed that 10 at.% of Lu³⁺ ( x = 0.1) has been able to stabilize GdAG against its thermal decomposition to a mixture of GdAlO₃ ( GdAP) and Al₂O₃ phases at temperatures above 1300°C and that Lu³⁺ doping effectively lowers the temperature for garnet crystallization. The precursors of x ≥ 0.3 convert to pure LnAG at a low temperature of ~1000°C via the intermediates of Ln₄Al₂O₉ ( LnAM) and LnAP. The carbonate precursors are loosely agglomerated and the resultant LnAG powders show good dispersion and a fairly uniform particle morphology. The (Gd,Lu)AG solid solutions exhibit decreasing lattice parameters and increasing optical bandgaps along with more Lu³⁺ incorporation. [ABSTRACT FROM AUTHOR]