STRUCTURAL AND MAGNETIC PROPERTIES OF Smx(Fe, Zr)100-x
I. Nehdi1, M. Abdellaoui1*, C. Djega-Mariadassou2, L. Bessais2, H. Zarrouk1
1National Institute of Research and Physic-chemistry Analyses, Technological Pole, 2020 Sidi Thabet, Tunisia
2Laboratoire de Chimie Métallurgique des Terres Rares, Glvt, 2 - 8 rue Henri Dunant, F-94320 Thiais Cedex, France
* Corresponding author. E-mail : mohieddine.Abdellaoui@inrap.rnrt.tn
Received :03 May 2002; revised version accepted : 02 February 2003
The Sm2Fe17Ny permanent magnet exhibits good magnetic properties. The precursor of this permanent magnet is the Sm2Fe17 phase which can be synthesized by arc melting, and subsequent annealing starting from a powder mixture of Sm and Fe, followed by an annealing at 1225 K. Nevertheless, the Sm2Fe17 phase can never be synthesized without the existence of a minora-Fe phase which affects the magnetic properties of the nitride Sm2Fe17Ny.
In this work, in a first step, we have tried to optimize the initial composition of SmxFe100-x in order to obtain a pure Sm2Fe17 phase. In a second step, we have studied the influence of the Fe substitution for Zr on the unit cell parameters of the 2 : 17 phase and on its Curie temperature. SmxFe100-x alloys with x = 10.52, 11.46, 12.37, 13.26, 14.14 and 15.00 at. % have been synthesized by arc melting. The structural analyses carried out by X-ray diffraction (XRD) using the Rietveld method show that when increasing the Sm excess, the residual proportion ofa-Fe decreases to reach less than 5 wt. % for Sm14.14Fe85.86. For higher Sm excess, the proportion of the residual a-Fe remains constant and equal to 5 wt. %. The structural analyses of the substituted alloys Sm2Fe17-yZry ( y = 0.5, 1 and 1.5), have shown that the substitution of Fe for 2.5 % at. Zr eliminates a-Fe and leads to the formation of a pure phase of Th2Zn17 type. The Sm2Fe16Zr1 sample shows the highest Curie temperature, 445 K. When the Zr content "y" exceeds the value 1.5, the rhombohedral phase with 2:17 type structure transforms into a monoclinic phase with P21/c space group of Nd3(Fe,Ti)29 type.
Keywords : Sm2(Fe, Zr)17 compound, arc melting, Magnetic properties.