The Solubility of Indium in Na₂Ga₇

Abstract

The ternary solid solution Na2Ga7–xInx (x ≤ 0.25) was synthesized by annealing the elements at 300 °C in sealed Ta ampoules. Differential thermal analysis (DTA) indicated incongruent phase formation. The peritectic temperature ranges from 501(2) °C (x = 0) to 474(2) °C (x = 0.25). In addition, the unit cell parameters increase significantly with In content. At its maximum of x = 0.25, the unit cell volume increases by 1% compared to Na2Ga7. The In positions are deduced from single‐crystal X‐ray diffraction data obtained for the composition Na2Ga6.95In0.05 (space group Pnma; Z = 8; a = 14.876(3) Å, b = 8.688(2) Å, c = 11.605(4) Å). In the crystal structure of Na2Ga7, which consists of Ga12 icosahedra and 4‐bonded Ga atoms, the In atoms solely substitute the latter. The Na atoms are located in the channels and cavities of the framework. With the formula unit [Na+]16[(12b)Ga122–]4[(4b)Ga–]7.6[(4b)In–]0.4, the phase is electron‐precise and can be considered a Zintl‐Wade compound.