Crystal chemistry and thermoelectric properties of Gd₂Te₃

Gd₂Te₃, M_r = 697.30, orthorhombic, Pnma, a = 12.009(9), b = 4.3012(6), c = 11.818(2) Å, V = 610.4(6) ų, Z = 4, D_m = 7.384, D_x = 7.59 g cm⁻³, Mo Kα, λ = 0.71069 Å, μ = 357 cm⁻¹, F(000) = 1136, room temperature, R = 0.033, 822 observed reflections. The redetermination confirms that Gd₂Te₃ is isostructural with Sb₂S₃ (stibnite). The reported solid-solution series Gd₂Te₃–Gd₃Te₄ does not exist. Gd–Te bond lengths vary from 3.104(1) to 3.240(3) Å and Gd is in sevenfold coordination. Gd₂Te₃ has a power factor S²/ρ = 0.6 × 10⁻⁶ V² K⁻² Ω⁻¹ cm⁻¹ at 1273 K. It is not suitable as a high-temperature thermoelectric material because it decomposes to GdTe which is metallic.