Search

Phase equilibria in the Hf–Ti–P system were investigated at T = 1070 K in the region 0–67 at.% 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 Hf x Ti 2− x P (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) A) and Hf x Ti 2− x P 0.68 . (0.75 ⩽ x ⩽ 1.00; Zn 3 Cu-type, space group Р -6, a = 4.758(1)–4.803(1), c = 3.005(1)–3.035(1) A). The crystal structure of the new phosphide Hf 5.35 Ti 8.65 P 8.93 was determined by X-ray single crystal diffraction. This compound crystallizes with the Zr 14 P 9 -type structure (space group Pnnm , cell parameters a = 15.973(1), b = 26.335(2), c = 3.5281(2) A, R 1 = 0.0670; wR 2 = 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.

Part of the quaternary Ce–Mn–In–Ge phase diagram has been examined through powder X-ray diffraction and energy-dispersive X-ray analysis. Two new quaternary (Ce 4 Mn 2 InGe 4 and Ce 2 Mn 2 InGe 2 ) and two ternary (Ce 3 Mn 2 Ge 3 and Ce 43 Mn 18 Ge 39 ) phases were found. The isothermal sections of the boundary ternary systems (Ce–Mn–In, Mn–In–Ge, Ce–In–Ge, and Ce–Mn–Ge) were determined at 800 °C. Among these, the Ce–Mn–Ge system deserves particular attention because the phase equilibria are complex. Relative to the previously reported phase diagram evaluated at a lower temperature (400 °C), three ternary phases (CeMn 2 Ge 2 , Ce 2 MnGe 6 , and CeMnGe) persist, Ce 2 MnGe 5 does not form, and two new phases with very close composition (Ce 3 Mn 2 Ge 3 and Ce 43 Mn 18 Ge 39 ) appear at 800 °C. Ce 3 Mn 2 Ge 3 (orthorhombic Hf 3 Ni 2 Si 3 -type) has a small homogeneity range (2%) deviating from the ideal composition, whereas Ce 43 Mn 18 Ge 39 (tetragonal La 2+ x MnGe 2+ y -type) has negligible homogeneity. Magnetic measurements on Ce 4 Mn 2 InGe 4 suggest ferromagnetic behaviour.

The ternary germanides RE 3 Mn 2 Ge 3 , which have been prepared by arc-melting and annealing at 800 °C, are formed with larger rare-earth components (RE = Ce–Nd), in contrast to other RE 3 M 2 Ge 3 series. They adopt the orthorhombic Hf 3 Ni 2 Si 3 -type structure (space group Cmcm , Z = 4). Single-crystal X-ray diffraction studies performed for the Ce member ( a = 4.3340(3) A, b = 11.6069(9) A, c = 14.6717(12) A) indicate an expanded structure relative to other RE 3 M 2 Ge 3 series, with essentially nonbonding Ge–Ge contacts between the [Mn 2 Ge 3 ] layers built up of double-chains of MnGe 4 tetrahedra. A minor oxidation product identified in the course of these investigations was proposed to be Nd 4 Mn 2 Ge 5 O 0.6 , in which a host monoclinic Yb 4 Mn 2 Sn 5 -type structure accommodates interstitial oxygen atoms partially occupying an octahedral void (space group C 2/ m , Z = 2, a = 16.275(3) A, b = 4.3779(8) A, c = 7.3783(14) A, β = 107.372(2)°). This structure also contains layers with double-chains of MnGe 4 tetrahedra which are now connected through Ge 2 dimers; isolated Ge atoms in square planar coordination are located between the layers. Magnetic measurements on RE 3 Mn 2 Ge 3 suggest complex antiferromagnetic ordering phenomena with several field-dependent transitions.

The interaction between components in the Zr–Ti–P system in the range of up to 67 at.% P was analyzed and the isothermal section diagram at 1070 K was constructed from X-ray structural and EDS analysis. Solid substitutional solutions based on the binary phosphides M 3 P with the Ti 3 P-type structure (Ti 3.0−2.3 Zr 0−0.7 P and Zr 3.0−2.5 Ti 0−0.5 P) were found. The phosphide (Ti,Zr) 2 P with the Co 2 Si-type structure is homogeneous at the Zr 1.2−0.6 Ti 0.8−1.4 P composition. From powder X-ray diffraction methods, the crystal structure of ZrTiP 0.68 was shown to be of the Zn 3 Cu-type (space group P -6, a = 0.47600(1), c = 0.30038(1) nm, R I = 0.0444); HfTiP 0.68 is isostructural. These compounds are homogenous in the range Zr 1.0−1.5 Ti 1.0−0.5 P 0.68 and Hf 0.9−1.2 Ti 1.1−0.8 P 0.68 . From single-crystal methods, the structure of Zr 0.93 Ti 0.07 P 0.93 was determined to belong to the WC-type structure (space group P -6 m 2, a = 0.3004(2), c = 0.3117(3) nm, R F = 0.0228).