Yu. D. Seropegin

Analysis of the melting temperatures of RT2 compounds (MgCu2 structure) (R=Rare Earth, TMn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) and RT2X2 compounds (RLa, Ce, Sm, Er; TMn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt; XSi, Ge)

Abstract Physico-chemical analysis techniques, including X-ray phase analysis and differential thermal analysis were employed for the characterisation of compounds including their melting temperature. The melting temperature for 70 RT 2 X 2 compounds has been measured (R=(La, Ce, Sm, Er, Tm), T=(Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt), X=(Si, Ge)). It is established, that the compounds CePt 2 Ge 2 , LaPt 2 Si 2 , LaPt 2 Ge 2 belong to the CaBe 2 Ge 2 structure type (group P4/mmm ): LaPt 2 Si 2 ( a =0.4280(2) nm, c =0.9831(6) nm); LaPt 2 Ge 2 ( a =0.4417(3) nm, c =0.976(2) nm) and CePt 2 Ge 2 ( a =0.44033(4) nm, c =0.9808(1)). An empirical model able to describe the melting temperature of T m of the compounds RT 2 , RT 2 X 2 with accuracy often better than 5% is presented: T m = const /V 1 3 , where the constant factor depends on the type of atoms constituting the compound, and where V is unit cell volume.

Peculiarities of the electrical double layer structure on renewed electrodes of eutectic alloys

Abstract Differential capacitance curves are measured on renewable electrodes of SnPb and SnCd eutectic alloys in the region of their ideal polarizability. It is shown that, upon the renewal of the electrode surface, the transients of the double layer capacitance are observed which indicate anomalously high surface-phase changes on electrodes. A model of the temporal effects observed is proposed and substantiated. According to this model, the surface enrichment with the surface-active alloy component proceeds via the mechanism of surface diffusion of this component from the areas enriched with it (boundaries of Sn crystal grains).

Investigation of phase relationships and physical properties of YbPdGe compounds

Abstract A variety of physicochemical analysis techniques were employed in constructing the isothermal cross-section of the phase diagram of the YbPdGe system 870 K. Several new ternary compounds Yb 10 Pd 75 Ge 15 , Yb 20 Pd 20 Ge 60 , Yb 2 PdGe 6 , YbPdGe 2 , YbPd 2 Ge, YbPdGe, YbPd 0.5 Ge 1.5 , Yb 33.3 Pd 28 Ge 38.7 and Yb 42 Pd 13 Ge 45 were detected. The temperature dependences of the specific electric resistance were investigated for the alloys on the basis of YbPdGe, YbPd 2 Ge and YbPd 2 Ge 2 compounds as well as for Yb(PdGe) 3 (alloy from the range of solid solutions based on YbPd 3 ).

Crystallographic data of new ternary Sm5Ge4-type R2Ti3Ge4 compounds (R=Gd-Er)

Abstract Investigations made by powder X-ray diffraction on five new ternary R2Ti3Ge4 compounds (R=Gd-Er) are reported. The (Gd0.97)2Ti3Ge4 (a=0.7042(1) nm, b=1.3494(2) nm, c=0.7186(1) nm), (Tb0.99)2Ti3Ge4 (a=0.7019(1) nm, b=1.3457(2) nm, c=0.7156(1) nm), (Dy0.97)2Ti3Ge4 (a=0.6987(1) nm, b=1.3409(2) nm, c=0.7122(1) nm), (Ho0.96)2Ti3Ge4 (a=0.6981(1) nm, b=1.3399(2) nm, c=0.7117(1) nm) and (Er0.91)2Ti3Ge4 (a=0.6962(1) nm, b=1.3367(2) nm, c=0.7099(1) nm) crystallize in the orthorhombic Sm5Ge4-type structure (space group Pnma).

Phase equilibria in the Sm{{Ru,Rh}}{{Si,Ge}} systems at 870 K

Abstract Physico-chemical analysis techniques, including X-ray phase analysis and electron probe X-ray analysis were employed in constructing the isothermal cross-section of the phase diagrams Sm{{Ru,Rh}}{{Si,Ge}} systems at 870 K. The formation of the new ternary intermetallic compounds, Sm2RuGe2, Sm2RhGe2 (structure type Zr2CoSi2); Sm3Ru2Si2, Sm3Rh2Si2, Sm3Rh2Ge2 (structure type La3Ni2Ga2); SmRh5Si3, SmRh5Ge3 (structure type UCo5Si3); Sm2Ru3Si5 (structure type Sc2Fe3Si5); SmRu3Si2 (structure type LaRu3Si2); SmRuSi3 (structure type BaAl4); Sm33Rh20Ge47 (structure type AlB2); Sm25Rh19Ge56 (structure type CeRh1 − xGe2 + x); Sm2RhGe6 (structure type Ce2CuGe6) and Sm62Ru28Ge10, SmRu3Si, Sm2RuSi2. Sm62Ru10Si28, Sm33Rh50Si17, Sm16Rh68Si16, SmRh3Si6, Sm37Rh35Si28, Sm2RhSi2, Sm4Rh4Si, Sm33Rh53Ge14, SmRh2Ge, Sm18Rh64Ge18, SmRh3Ge6, were detected in Sm(Ru,Rh)(Si,Ge) systems. It was found that compound SmRuSi does not belong to the structure type PbFCl. Ternary compound SmRuGe was not found in SmRuGe system at 870 K.

Phase equilibria in the TiNbGe system at 1170 K

Abstract Physico-chemical analysis techniques, including studies of microstructure, X-ray phase analysis, electron microprobe, high-temperature differential thermal analysis and measurements of hardness, microhardness and specific electrical resistance, are applied to study the interaction between the components in the TiNbGe system. The phase diagram for the TiGe system has been refined. The compound Ti 5 Ge 3 melts congruently at 2250 K. The germanides Ti 6 Ge 5 and TiGe 2 are formed by peritectic reactions at 1920 and 1345 K, respectively. An isothermal section of the TiNbGe phase diagram corresponding to 1170 K is constructed and homogeneity regions for ternary niobium and titanium germanide solid solutions are reported. No ternary compounds occur in the system. A polythermal phase diagram section along the quasi-binary Ti 5 Ge 3 nNb 5 Ge 3 section is given. The mechanical and electrical properties of a number of alloys are described.

New Ternary Compounds R117Fe52Ge112 (R = Gd, Dy, Ho, Er, Tm) and Sm117Cr52Ge112 of the Tb117Fe52Ge112-Type Structure

Abstract The new compounds Gd117Fe52Ge112 [a = 2.8711(4) nm], Dy117Fe52Ge112 [a = 2.8398(5) nm], Ho117Fe52Ge112 [a = 2.8293)(5) nm], Er117Fe52Ge112 [a = 2.8108(7) nm], Tm117Fe52Ge112 [a = 2.802(2) nm], and Sm117Cr52Ge112 [a = 2.9098(6) nm] belonging to the Tb117Fe52Ge112-type structure (space group Fm3m) were prepared and characterized using powder X-ray diffraction.

Crystal structure of the new compound Ce3Pt23Si11

Abstract The crystal structure of the new ternary compound, Ce 3 Pt 23 Si 11 , was determined by X-ray analysis of a single crystal (Enraf-Nonius CAD-4 diffractometer, Mo Kα radiation, 585 independent reflections, R =0.0487). The Ce atoms have only one crystallographic position with a very rare tetragonal prism coordination polyhedron.

Crystal structure of the new compound Ce3Pt23Ge11

Abstract The crystal structure of the compound Ce3Pt23Ge11 has been determined by X-ray analysis of a single crystal (Enraf-Nonius CAD-4 autodiffractometer, Mo Kα radiation, 276 independent reflections, R-factor 0.0735 in isotropic approximation). This structure has been found to belong to a new structural type: space group F 4 3m, a = 17.1833(9) A , Z = 8 . The coordination polyhedra of the cerium atoms are compressed cubes, those of platinum have eight or 10 apexes and those of germanium are either trigonal prisms with an additional atom or cubes. The magnetic properties of Ce3Pt23Ge11 at low temperatures (4–100 K) were investigated. A diffuse magnetic phase transition at around 10 K was detected.

GdTiGe (CeScSi-type structure) and GdTiGe (CeFeSi-type structure) as the coherent phases with different magnetic and hydrogenization properties

Abstract The results of investigations of new ternary coherent GdTiGe compounds and corresponding hydrides by X-ray powder diffraction and magnetic measurements are reported. Coherent phases GdTiGe with CeScSi-type structure and GdTiGe with CeFeSi-type structure were found to coexist in the GdTiGe alloy when the sample mass was 5 g (melting in electric arc furnace in argon atmosphere). Annealing at 1070 K for 200 h in argon atmosphere led to an increase in GdTiGe (CeScSi-type structure) phase in the GdTiGe alloy. The GdTiGe with CeScSi-type structure ( a = 0.4065(1), c = 1.5450(1) nm) was characterized by Curie point T c = 376 K, while GdTiGe with CeFeSi-type structure ( a = 0.4065(1), c = 0.7716(1) nm) demonstrated Neel point T N = 412 K. The mechanical hydrogenization of the GdTiGe alloy led to formation of the GdTiGeH ∼4 hydride with CeScSi-type structure and to a sharp decrease in magnetization; GdTiGe with CeFeSi-type structure remained passive. The X-ray single crystal diffraction study confirmed that the Gd(Ti 0.8 Zr 0.2 )Ge compound has the CeScSi-type structure (space group I 4/ mmm , a = 0.4060(1), c = 1.5400(3) nm).