Phase relations of the Ag-Ga-N system

The phase diagram of the Ag-Ga binary system and the phase relations of the Ag-Ga-N system are studied by DTA and X-ray powder diffraction. The equilibrium phase diagram of the Ag-Ga system is reconstructed. Two intermetallic phases are determined in the Ag-Ga system: the Ag2Ga compound and a novel δ-Ag3Ga2 with the composition about 40 at.% Ga. The novel phase δ-Ag3Ga2 which is the product of the peritectic reaction Ag2Ga + L ↔ δ-Ag3Ga2 at 575 K is indexed with an orthorhomic lattice with lattice parameters a = 6.7276(2) Å, b = 3.8840(1) Å, c = 3.2200(1) Å and V = 84.14 Å3. The temperature-dependent lattice parameters of ζ′-Ag2Ga with 28 at.% Ga are measured by temperature-dependent X-ray powder diffraction from 93 to 543 K. The linear temperature dependences of the expansion coefficients along the direction of a- and c-axis and volume coefficients are obtained, αa = (1.4741 + 0.0028T) × 10−5, αc = (1.1710 + 9.1349 × 10−4T) × 10−5 and αV = (4.1167 + 0.0065T) × 10−5, respectively. No ternary phase is found in the Ag-Ga-N system and no solubility of Ag in GaN is observed under the present experimental conditions.