The phase equilibria and crystal structure of the phases in the Hf–Ti–P system

Abstract

Phase equilibria in the Hf–Ti–P system were investigated at T=1070K in the region 0–67at.% of P, employing X-ray powder diffraction. The three ternary compounds exist in the Hf–Ti–P system at this temperature. Two of them have homogeneity regions and their compositions can be represented as HfxTi2−xP (0.65⩽x⩽1.30; TiNiSi-type, space group Pnma, a=6.130(3)–6.673(5), b=3.508(2)–3.557(2), c=8.050(5)–8.161(2)Å) and HfxTi2−xP0.68. (0.75⩽x⩽1.00; Zn3Cu-type, space group Р-6, a=4.758(1)–4.803(1), c=3.005(1)–3.035(1)Å). The crystal structure of the new phosphide Hf5.35Ti8.65P8.93 was determined by X-ray single crystal diffraction. This compound crystallizes with the Zr14P9-type structure (space group Pnnm, cell parameters a=15.973(1), b=26.335(2), c=3.5281(2)Å, R1=0.0670; wR2=0.0875). The majority of binary compounds form substitution type solid solutions, in their homogeneity ranges the substitution of Ti by Hf or Hf for Ti takes place.