C.H. Wu

STRUCTURE AND MAGNETOSTRICTION OF DY0.9-XPRXTB0.1FE2 PSEUDOBINARY COMPOUNDS

The melting behaviour, structure, Curie temperature and magnetostriction of the pseudobinary compounds Dy0.9-xPrxTb0.1Fe2 were investigated. These compounds are essentially single phase with cubic Laves structure. All these compounds contain a trace of a second phase when x less-than-or-equal-to 0.4. Beyond x > 0.6, a non-cubic phase appears. The Curie temperature decreases steadily with increasing x. The maximum magnetostriction exists near x = 0.1.

STRUCTURE AND MAGNETIC-PROPERTIES OF THE PSEUDOBINARY COMPOUNDS PR(CO1-XMX)5

The structure of the pseudobinary compounds Pr(Co1−xMx)5 (M ≡ Ni, Fe, Mn, Cr, V, Ti) and the magnetic properties of the Pr(Co1−xNix)5 compounds in particular were investigated. A continuous solid solution with a CaCu5-type structure forms after homogenization at 1000 °C when M is nickel. The homogeneous range is restricted when M is a metal other than nickel. A second phase, which is tentatively identified as Pr5(Co,M)19, is formed beyond this limit. n nThe composition dependences of the lattice constants, the Curie temperature and the room temperature saturation magnetization of Pr(Co1−xNix)5 compounds were studied. The results obtained indicate that certain correlations exist between the composition dependences of the lattice constants and the magnetic properties.

Structure and decomposition behaviour of GdCo5−xMx pseudobinary compounds I: Structure

The structure of the pseudobinary compounds GdCo5−xMx (M ≡ Cu, Al, Ga) was investigated. The homogenized GdCo5−xCux compounds form continuous solid solutions with the CaCu5-type structure up to x = 4. The homogeneous range is much more restricted when M is either aluminium or gallium. The composition dependences of the lattice constants of these three systems were studied. It was found that the copper atoms of the GdCo5−xCux system (x < 2) preferentially occupy the 2c site of the CaCu5− type hexagonal lattice.

Structure and magnetic properties of cobalt-rich Pr-Co-B alloys

Abstract The structure and lattice constants of six Pr-Co-B ternary compounds (Pr 2 Co 14 B, PrCo 4 B, Pr 3 Co 11 B 4 , Pr 2 Co 7 B 3 , PrCo 12 B 6 , PrCo 4 B 4 ) have been studied. Detailed powder X-ray diffraction data for PrCo 4 B 4 are given. The anisotropy constants, anisotropy fields and Curie temperatures of Pr 2 Co 14 B, PrCo 4 B, Pr 3 Co 11 B 4 and Pr 2 Co 7 B 3 compounds have been determined.

An investigation of the metastable character of Y(Co,M)5 compounds

The decomposition behaviour of YCo5, YCo4Ni, YCo3Ni2, YCo4Cu, YCo4Al and YCo4.8M0.2 (M ≡ Ti, V, Cr, Mn, Fe) in the temperature range 635–800 °C was investigated by optical metallography, electron microprobe and X-ray diffraction techniques. It was found that the substitution of one cobalt atom by nickel or aluminium in YCo5 lowers the decomposition temperature. Nevertheless, the substitution of 0.2 atoms of cobalt by titanium, vanadium, chromium, manganese or iron markedly affects the stability of the CaCu5 structure. The decomposition of YCo4Cu at 700 °C is characterized by grain boundary and general precipitation of the (2:17) phase. The decomposition at 800 °C of YCo4.8Ti0.2 and YCo4.8V0.2 was found to be similar to the classical eutectoid decomposition and is characterized by the simultaneous formation of parallel lamellae of the (2:17) and (2:7) phases. However, under identical heat treatment conditions the other three compounds (YCo4.8Cr0.2, YCo4.8Mn0.2 and YCo4.8Fe0.2) exhibit a monophase eutectoid reaction.

Structure and magnetic properties of Gd(Co1−xNix)5 compounds

Abstract The lattice constants, Curie temperature and magnetization of the pseudo-binary system Gd(Co1−xNix)5 were determined as functions of composition. The microstructure of the as-cast samples is duplex for x ⩽ 0.5; the annealed samples are single phase with a CaCu5-type hexagonal structure. The composition dependence of the lattice constants of Gd(Co1−xNix)5 compounds does not obey Vegards law. Compensation points were observed in the magnetization versus temperature curves for compounds with x ⩽ 0.6; however, they vanish at x = 0.8. These findings are elucidated in the light of the currently accepted ferrimagnetic coupling scheme.

Structure and magnetostriction of (Dy0.65Tb0.25Pr0.1)(Fe1−xAlx)3 alloys

The structure, Curie temperature and magnetostriction of (Dy0.65Tb0.25Pr0.1)(Fe1-xAlx)(3) (0 less than or equal to x less than or equal to 0.30) alloys were investigated using optical microscopy, X-ray diffraction, electron probe microanalysis, vibrating sample magnetometer and standard strain gauge techniques. It was found that these alloys are multiphase. When x less than or equal to 0.10, the main phase possesses the PuNi3-type rhombohedral structure and becomes CeNi3-type hexagonal when x>0.25. When 0.10<x less than or equal to 0.25, both structures coexist. A minor phase (Dy,Tb,Pr)(6)(Fe,Al)(23) exists in all alloys, which increases with increasing Al content. The Curie temperature and the room-temperature magnetostriction of the (Dy0.65Tb0.25Pr0.1)(Fe1-xAlx)(3) alloys decrease with increasing Al substitution for Fe.

Study of the 1050 °C isothermal section of the ternary system YCoFe

Abstract The isothermal section at 1050 °C of the ternary system Y-Co-Fe was determined by diffusion couple and electron microprobe techniques supplemented by optical microscopy, X-ray diffraction and thermal gravimetric analyses. The 1050 °C isothermal section of this system consists of nine single phases: α(1:2), β(1:3), θ(2:7), ξ(5:19), λ(6:23), τ(1:5), η(1:6), π(2:17) and γ(Co-Fe-Y solid solution); twelve two-phase regions: α + β, β + θ, β + λ, θ + λ, θ + ξ, ξ + τ, λ + η, λ + π, τ + η, τ + π, η + π, π + γ; and six three-phase regions: θ + ξ + τ, β + θ + λ, θ + λ + θ, τ + η +θ, λ + η + π, τ + π + η. The structure and homogeneity range of the principal phases in the transition metal-rich portion were carefully studied.

Structure and Magnetic Properties of Ho2Co17‐xMx Pseudobinary Compounds.

Abstract The homogeneity range of the pseudobinary system Ho 2 Co 17− x M x (M ≡; Ni, Fe, Mn, Cr, V, Ti, Cu, Al) and the dependence of the lattice constants and the Curie temperature on composition were studied. Although Ho 2 Co 17 , Ho 2 Ni 17 and Ho 2 Fe 17 have identical crystal structures and similar lattice constants, the homogeneity range for the Th 2 Ni 17 -type compound in the Ho 2 Co 17− x Ni x and Ho 2 Co 17− x Fe x systems is limited to x versus composition have maxima at x values of 1, 3 and 0.9 for the systems Ho 2 Co 17− x Ni x , Ho 2 Co 17− x Fe x and Ho 2 Co 17− x Cu x respectively. This suggests that the effect of nickel, iron and copper on the Co-Co exchange interaction in the cobalt sublattice at low concentrations may be different from that at high concentrations.

Isothermal decomposition behaviour of CeCo5+x compounds

The stability and decomposition behaviour of CaCu5-type CeCo5 + x compounds (0.1 less-than-or-equal-to x less-than-or-equal-to 1) at 650-degrees-C and 750-degrees-C have been investigated using optical microscopy, scanning electron microscopy, X-ray diffraction and electron probe microanalysis techniques. The homogeneity range of this CaCu5-type CeCo5 phase at 1000-1100-degrees-C has been assessed to be from 83.6 to 85.7 at.% Co (CeCo5.1-CeCo6). When the cobalt concentration is close to the lower limit of high temperature homogeneity range (83.6 at.% Co), only CeCo5-Ce5Co19 phase boundary precipitation of Ce2Co17 takes place; when the cobalt concentration is lower than the congruently melting composition (85.0 at.% Co), its decomposition behaviour is identical to that of the stoichiometric RCo5 compounds (R = Pr, Gd, Y). When the cobalt concentration is equal to or higher than 85.0 at.% Co, the decomposition behaviour of the grain boundary is essentially the same as that of the compound whose cobalt concentration is lower than 85.0 at.% Co, the intragranular decomposition is of the spinodal mode, and the parent phase (CeCo5.56 or CeCo6) decomposes into Ce2Co17 and isomorphous CeCo4.93.