A composition is provided that includes a plurality of calcined particles of terbium aluminum oxide having a mean particle domain size of between 30 and 600 nanometers. A translucent article having a surface includes polycrystalline terbium aluminum garnet having a mean grain size from 1 to 10 microns and light scattering inclusions of aluminum-rich oxide and/or terbium-rich oxide that are present at less than 2 surface area percent of the surface. A process for forming such an article involves sintering the above provided composition at a temperature between 1500.degree. C. and 1700.degree. C. to yield a sintered article. The article has improved translucency and even transparency as sintering is performed under vacuum at a temperature between 1610.degree. C. and 1680.degree. C. Hot isostatic pressing alone or in combination with article polishing also improves article translucency.