Phase relationship, microstructure and magnetocaloric effect in Gd1-x(Si0.5Ge0.5)(x) alloys

Microstructure and magnetocaloric effect were investigated in Gd1-x(Si0.5Ge0.5)(x) alloys with x = 0.38, 0.41, 0.45, 0.47 and 0.50. The phase identification and compositional analysis were carried out by a combination of x-ray powder diffraction, scanning electron microscopy and electron probe microanalysis. The Gd-5(Si,Ge)(4) phase was found to have an orthorhombic Gd5Si4-type structure when the coexisting phase was Gd-rich (Gd5Si3-type) and a monoclinic Gd5Si2Ge2-type structure when the coexisting phase was Gd-depleted (Gd5Ge5-type). The magnetocaloric effect was found to depend on the volume fraction and the Si/Ge ratio of the ferromagnetic 5 : 4 phase in the above series of alloys. A maximum magnetocaloric effect ( Delta S) M of 14.3 J kg(-1) K-1 for a magnetic field change from 0 to 5 T was obtained for the x = 0.45 alloy.