The isothermal section at 400  C of the Pr–Ag–Sn ternary system D. Mazzone, P. Riani, G. Zanicchi, R. Marazza, R. Ferro* Dipartimento di Chimica e Chimica Industriale, Sezione di Chimica Inorganica e Metallurgia, Universita ` di Genova, Via Dodecaneso 31, 16146 Genova, Italy Received 3 May 2002; accepted 15 May 2002 Abstract The phases and equilibria involved in the isothermal section at 400  C of the Pr–Ag–Sn ternary system have been here investi- gated after different annealing times by X-ray diffraction, optical and scanning electron microscopy and electron probe micro- analysis. Three ternary compounds have been confirmed: PrAgSn hP6 LiGaGe type, Pr 3 Ag 4 Sn 4 oI22 Gd 3 Cu 4 Ge 4 type and Pr 5 AgSn 3 hP18Hf 5 CuSn 3 type. The solid solubility ranges of the binary compounds have been considered and trends of their lattice parameters studied. The tie-triangles of the ternary system have been defined. The general features of the section are discussed and compared to those of the other R–Ag–Sn ternary systems. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Rare earth intermetallics; A. Ternary alloy systems; B. Crystallography; B. Phase diagram; B. Phase identification 1. Introduction The ternary alloys R–T–X of the rare earth metals R, a transition element T and an element X belonging to the last groups of the periodic table have been carefully investigated since their compounds could present inter- esting properties. Their behaviour in high magnetic fields, the magnetic ordering studied by neutron dif- fraction techniques, the crystal structures, thermo- dynamic and electrical transport properties and 119 Sn Mo¨ssbauer spectroscopy are currently under investiga- tion. A systematic study on the existence fields and the equilibria involved in the formation of particular groups of phases, such as those belonging to the R-(Cu,Ag,Au)- X systems, could also be important. A contribution has previously been made by our research group with stud- ies on R–Cu–Sn (R=Ce, Pr, Nd, Yb) [1–4], R–Ag–Sn (R=Ce, Yb) [5,6] and Ce–Au–Sn [7] isothermal sec- tions. In this paper the isothermal section at 400  C of the Pr–Ag–Sn ternary system is presented and discussed. 2. Literature data 2.1. Binary systems 2.1.1. Ag–Sn This well known system has been described in Mas- salski [8] mainly on the basis of the assessment per- formed by Karakaya and Thompson [9]. Subsequently Chevalier[10], Kattner[11] and then Xie [12] and Oh [13] re-optimized the diagram, improving the agreement between the calculated phase diagram and the assessed phase boundaries. 2.1.2. Ag–Pr The diagram is reported in Massalski on the basis of an assessment carried out by Gschneidner and Calder- wood [14,15]. The following compounds were reported: PrAg 5 , Pr 14 Ag 51 , with a homogeneity range from approximately 22–25 Pr at.%, a and bPrAg 2 and PrAg. These compounds have been substantially confirmed in this work, apart from the richest Ag compound which showed a stoichiometry that was slightly richer in Pr. Thus, the Pr 2 Ag 9 formula, the same as that observed in the Ce–Ag alloys in the investigation on the Ce–Ag–Sn ternary system, has been accepted in this work. 0966-9795/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0966-9795(02)00056-0 Intermetallics 10 (2002) 801–809 www.elsevier.com/locate/intermet * Corresponding author. Tel.: +39-010-353-6149; fax: +39-010- 362-5051. E-mail address: ferro@chimica.unige.it (R. Ferro).