THERMODYNAMIC PROPERTIES OF PLATINUM-RICH INTERMETALLICS IN THE PT-GD SYSTEM

Phase relations in the Pt-GdPt portion of the system have been determined at 1100 K by X-ray and microscopic examination of quenched samples equilibrated for 610 ks. Five compounds have been identified; GdPt5, ‘GdPt3′, GdPt2, Gd3Pt4 and GdPt. The phase GdPt3 with AuCu3 type structure has not been reported earlier. The compound GdPt3 is nonstoichiometric with a homogeneity range extending from 23 to 28 mol% Gd. The phase GdPt2 has a narrower nonstoichiometric range varying from 32 to 33 mol% Gd. The relative partial Gibbs' energy of Gd in the two-phase fields has been determined in the temperature range 925-1125 K using solid state galvanic cells incorporating single crystal CaF2 as the solid electrolyte and an equimolar mixture of Gd + GdF3 as the reference electrode. The Gibbs' energy formation of the intermetallic phases per mol has been derived from these measurements:$. © 1990, The Japan Institute of Metals. All rights reserved.