EFFECT OF ALUMINUM ON PHASE-STABILITY IN THE GD3CO11(B,AL)(4) SYSTEM

In the Gd3Co11B4-xAlx alloys the ternary 3:11:4 phase with Ce3Co11B4 s tructure is formed with an Al content x approximate to 0.5 substitutin g for boron. The fraction of this phase decreases as the boron content decreases in the samples. The Al, Co and Gd in excess form Gd(Co,Al)( 5) with CaCu5-type structure, and the fraction of this phase increases with increasing x. X-ray diffraction results show that these phases a re not at equilibrium. A strong preference of aluminium for the 3g sit e in the CaCu5-type structure is determined by Rietveld refinement of the X-ray diffraction pattern of the end-series compound (x = 4). (C) 1997 Elsevier Science S.A.