This study looked at the thermal conductivity of translucent (Y_1−xGd_x)₂O₃ (where 0 ≤ x ≤ 1) solid solution ceramics in the temperature range from 50 K to 300 K. The samples were obtained by hot pressing from high-purity nanopowders at 1600 °C, no sintering additives were used. Compositions with cubic syngony (x ≤ 0.7) and a monoclinic one (x ≥ 0.9) were investigated. Furthermore, a dense sample of cubic Gd₂O₃ with a LiF sintering additive was obtained and its thermal conductivity was determined (k = 11.7 W/(m K) at 300 K). It was shown that in the range of solid solution ceramic compositions 0.2 ≤ x ≤ 0.7, the thermal conductivity was practically unchanged and close to the value k ≈ 5 W/(m K) at 300 K.

Transparent ceramics based on thulium-doped cubic gadolinia Gd₂O₃ and its solidsolutions (Gd,Y)₂O₃, (Gd,Lu)₂O₃ and (Gd,Y,Lu)₂O₃ are fabricated by hot pressing. They feature low phonon energies and broad and smooth gain profiles extending above 2 μm.