In one embodiment, a method includes forming a powder having a composition with the formula: AhBiCjO12, where h is 3 ± 10%, i is 2 ± 10%, j is 3 ±10%, A includes one or more rare earth elements, B includes aluminum and/or gallium, and C includes aluminum and/or gallium. The method additionally includes consolidating the powder to form an optically transparent ceramic, and applying at least one thermodynamic process condition during the consolidating to reduce oxygen and/or thermodynamically reversible defects in the ceramic. In another embodiment, a scintillator includes (Gd3-a-cYa)x(Ga5-bAlb)yO12Dc, where a is from about 0.05-2, b is from about 1-3, x is from about 2.8-3.2, y is from about 4.8-5.2, c is from about 0.003-0.3, and D is a dopant, and where the scintillator is an optically transparent ceramic scintillator having physical characteristics of being formed from a ceramic powder consolidated in oxidizing atmospheres.
