Synthesis and magnetic properties of PrFe11V1−xTix and their nitrides

Abstract

We have succeeded in synthesizing PrFe11V1−xTix (x=0.2–1) compound and their nitrides with the ThMn12-type structure. The phase formation and magnetic properties have been investigated by x-ray diffraction, differential thermometric analysis, and magnetic measurement. The stable temperature range of the 1-12 phase for PrFe11V1−xTix alloys has been determined as a function of Ti content. PrFe11V compounds with the ThMn12-type structure do not exist and PrFe11Ti compounds with the TnMn12-type structure are obtained by annealing in a narrow temperature range between 1303 and 1383 K. Furthermore, 1-12 phase with the ThMn12-type structure can be obtained at lower temperature and wider temperature range with decreasing Ti content x (0.2⩽x⩽1). PrFe11V1−xTixNy with x=0.2–1 has a Tc of about 730–785 K, Ba larger than 8 T and Ms in the range 144–148 emu/g. These intrinsic magnetic properties are highly favorable for permanent magnet applications. As a preliminary, an intrinsic coercivity of 5.4 kOe is obtained for PrFe11V0.5Ti0.5Ny at room temperature by using mechanical alloying technique.

Phase transformation, structure and magnetic properties of (Nd,Pr)–Fe–V–B alloys and their nitrides prepared by mechanical alloying

“…Obviously the above results of Pr 10 Fe 76 V 6+y B 8Ày series are much different from those of Nd-containing counterparts as reported in previous work [16]. The reasons for poor magnetic properties induced by the excessive V are as follows: First, V is hard to be stabilized with Pr to form the Pr(Fe,V,B) 12 phase with ThMn 12 -type structure, as reported in previous work [22,23]. Second, the nitrogenation is not complete so that an amount of Pr(Fe,V,B) 12 phase exists even after nitrogenation, which has easy-plane anisotropy.…”

Metastable phases in rare-earth permanent-magnet materials

“…In the systems Nd x Fe 92−x Ti 8 and Nd 8 Fe 92−x Ti x , the Nd-Fe-Ti intermetallic compound with ThMn 12 -type structure has been successfully synthesized by mechanical alloying and subsequent annealing (Jin et al 1996(Jin et al , 1997. The hexagonal TbCu 7 -type structure is formed for Nd 8 Fe 84 Ti 8 alloys prepared by mechanical alloying and annealing at 650-850 • C. Increasing the annealing temperature promotes the transformation of Nd(Fe, Ti) 7 phase to Nd(Fe, Ti) 12 phase.…”

“…The diffusion mechanism for N atoms in the R 2 Fe 17 lattice is a chemical reaction diffusion rather than a freediffusion process (Zhang et al 1995). The relationship of the crystallographic structure and the intrinsic magnetic properties to the nitrogen content of NdFe 10.5 V 1.5 N x , PrFe 10.5 V 1.5 N x and PrFe 11 V 1−x Ti x N y was investigated by Yang et al (1998), Mao et al (1997), Tang et al (1997). The domain structures of NdFe 10.5 Mo 1.5 and NdFe 10.5 Mo 1.5 N x were studied by using magnetic force microscopy (Yang et al 1997b).…”

“…The Curie temperature of the mechanically alloyed Nd-Fe-Ti powders gradually changes from 180 • C for the TbCu 7 -type structure at an annealing temperature T a = 650 • C to 300 • C for the ThMn 12 -type compound at T a = 1050 • C (Jin et al 1996(Jin et al , 1997. After nitrogenation, the Curie temperature of the nanocrystalline compounds significantly increases to above 430 • C.…”

“…The magnetic properties of mechanically alloyed samples based on the Nd(Fe, Ti) 12 N x phase are unsatisfactory for practical purposes although the intrinsic magnetic properties of this compound are very attractive for permanent magnet applications (Jin et al 1996(Jin et al , 1997. The maximum values, i H c = 2.3 kOe, B r = 5.8 kG, (BH ) max = 3.2 MGOe, were attained for Nd 9 Fe 83 Ti 8 annealed at 960 • C for 30 min and nitrided at 400 • C for 15 h. This is mainly attributed to the improper growth and the presence of an excessive amount of α-Fe.…”