Ellouze, M.

Ezekwenna, Peter C.

I\u27Héritier, Ph.

James, William Joseph

Luo, R.

Marasinghe, G. K.

Von Dreele, R. B.

Yelon, William B.

Zhao, Yusheng S..

English

Missouri University of Science and Technology (Missouri S&T): Scholars' Mine

Missouri University of Science and Technology Scholars' Mine Physics Faculty Research & Creative Works Physics 01 Jan 1998 Pressure Induced Reversal of the Volume Expansion Caused by Interstitial Nitrogen in Nd₂Fe₁₇N₃ R. Luo William B. Yelon Missouri University of Science and Technology, yelonw@mst.edu Yusheng S.. Zhao M. Ellouze et. al. For a complete list of authors, see https://scholarsmine.mst.edu/phys_facwork/379 Follow this and additional works at: https://scholarsmine.mst.edu/phys_facwork  Part of the Chemistry Commons Recommended Citation R. Luo et al., "Pressure Induced Reversal of the Volume Expansion Caused by Interstitial Nitrogen in Nd₂Fe₁₇N₃," Institute of Electrical and Electronics Engineers (IEEE), Jan 1998. The definitive version is available at https://doi.org/10.1109/INTMAG.1998.742175 This Article - Conference proceedings is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in Physics Faculty Research & Creative Works by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact scholarsmine@mst.edu. ABSTRACT 205 sures between 0.5 bar an 8 bar by means of hydrogen differential thermal analysis (HDTA) showed, that the disproportionation reaction becomes stronger and proceeds at lower temperatures for increasing hydrogen pres- sures. X-ray diffractioninvestigations of the HDTA samples showed a de- creasing content of the 2: 17 phase for increasing hydrogen pressures, lead- ing to a completely disproportionated structure for all the compounds under investigation at 8 bar. Microstructural changes within the dispropor- tionated mixture as a result of the applied pressure have been documented in detail by high resolution scanning electron microscopy. The complete disproportionation of the samples with high Ga content is very promising for an application of the HDDR process under increased hydrogen pres- sures for the preparation of highly stable and coercive gas carbonated Sm2Fe17-,Ga,C, powders, which could be used for the production of fully dense permanent magnets by hot compaction. 'M. Kubis, L. Cao, A. Handstein, B. Gebel, K.-H. Muller, and L. Schultz 3. Appl. Phys. 81, 6485 (1997). 9:48 ED-05. THE HARD-MAGNETIC PROPERTIES OF MELT-SPUN Sm2Fe15Ga2C1.5 AND SmFel5-xMxCa2C1.5 (M=Cu, Nb; OS(X(2.0) ALLOYS*. Shao-ying Zhang, Bao-gen Shen, and Hong-wei Zhang (State Key Lab. of Magnetism & Ctr. for Condensed Matter Phys., Inst. of Phys., Chinese Acad. of Sci. , Beijing 100080, P.R. China) Our group has reported previously that the coercivity of 1.5T could be obtained in Sm2Fe14Ga3C1.5 ribbons by direct quenching at the optimum wheel velocity. Recently, it was discovered that the coercivity up to 2.2T could be achieved in melt-spun Sm2+(Fe15Ga2C2 with over- stoichiometric Sm content by annealing the amorphous ribbonsl. In this paper, the coercivity and microstructure of melt-spun Sm2Fe15Ga2C1.5 and SmFel5-xMxGdC1.5 (M=Cu,Nb; OS(x(2.0) alloys have been stud- ied as a function of composition and annealing temperature and time. The as-quenched almost amorphous ribbons were annealed at 823-1 173K. Be- fore annealing, the ribbons showed low coercivity (<O.ST). After anneal- ing, the ribbons with the main phase of Th2Zn17 and a small amount of (-Fe were detected from X-ray diffraction patterns and SEM. The coer- civities of all ribbons first increase monotonically with increasing anneal- ing temperature. The maximum coercivities at room temperature is about 1.4T. 2.2T and 1.6T for Sm2Fe15Ga2C1.5, SmFel4CulGa2C1.5 and SmFe14NblGa2C1.5, respectively, after annealing at 1073K for 15min. Then coercivities decrease at the higher annealing temperature. For SmFel4Cu 1Ga2C1.5 ribbons annealing at 1073K for 5-60min.. the maxi- mum coercivities were obtained between 15min. and 20min. Although the substitution of Cu or Nb for Fe has a small effect on the average size of crystalline grain, but affects the coercivity obviously. From the initial magnetizing curves and the applied magnetic field dependencies of Hc and MrMrmax, the mechanism of the coercivity has been analyzed. *This work was supported by the National Natural Science Foundation of China. 'J. van Lier, M. Seeger, and H. Kronm (ler, J. Magn. Magn. Mater. 167, 43 (1997). 1000 ED-06. ELECTRON MICROSCOPY STUDIES OF HIGH COERCIVE MELT-SPUN Sm,, ,@elSGaZC2 PERMANENT MAGNETS. J. van Lier, A. am, H. Labitzke, J. Thomas, M. Seeger, and H. Kronmuller (Max-Planck-Inst. fiir Metallforschung, Ueisenbetgstrasse 1 ,  D-70569 Stuttgm, Germany) The influence of overstoichiomebic Sm contents on the magnetic proper- ties of melt-spun Ga stabilized SmzFe17 carbides has been investigated. For optimum heat treated Sm2+&15GazCz ribbon flakes an increase of the room temperature coercivity could be observed from poHC= 1.7 T for stoichiometric samples to poHc=2.2 T for 6=0.15. This effect is very interesting because of an improved temperature stability. At 500 K a maxi- mum energy density of (BH),,,=31.4 H/m3 for 6=0.13 can be ob- served. It is shown, that a Sm rich nonmagnetic intergranular phase de- couples the grains magnetically and is consequently the reason for the high coercivities of these samples. Electron microscopy studies of these melt-spun Sm2+ #e15GazC2 samples with different Sm contents have been performed by SEM and TEM. A broad grain size distribution (50-250 nm) is observed in the SEM, but there is no difference between samples with different Sm contents. TEM studies show no change in grain shape with variation of the S value. High resolution TEM studies indicate the existence of a very thin intergranular phase for samples with an excess of Sm. To prove this we performed high resolution EDX studies with a scanning-TEM. These investigations show a significant increase of the Sm content at the grain boundaries for these high coercive samples. 10:12 ED-07. PRESSURE INDUCED REVERSAL OF THE VOLUME EXPANSION CAUSED BY INTERSTITIAL NITROGEN IN Nd2Fe17N3. G. K. Marasinghe, W. J. James, P. C. Ezekwenna (Univ. of Missouri-Rolla, Rolla, MO 65409). Robert Luo, W. B. Yelon (Univ. of Missouri Res. Reactor, Columbia, MO 6521 I ) ,  Y. Zhao, R. B. Von Dreele (Los Alamos Natl. Lab., Los Alamos, NM 87545). M. Ellouze, and Ph. 1'Heritier (ENS Physique de Grenoble, BP 46,38402 St. Martin d'Heres, France) Crystallographic properties of Nd2FeI7N3 have been investigated using powder neutron diffraction techniques at sample pressures up to 7.23 GPa. With increasing sample pressure, the unit cell volume of NdzFe17N, de- creases almost linearly at a rate of 6.1 A3/GPa without undergoing a phase transformation or expelling the interstitial nitrogen atoms. At 7.3 GPa, the unit cell volume of NdzFe17N3 becomes approximately equal to that of NdZFel7 at atmospheric pressure. Even though the unit cell of NdzFe17 expands anisotropically due to nitrogenation, contraction of the NdzFe17N3 unit cell under pressure appears to be isotropic with both a and c lattice parameters decreasing by approximately 1.8% as the sample pres- sure increases from ambient to 7.3 GPa. I 1024 ED-08. A NEUTRON DIFFRACTION STRUCTURAL STUDY O F  R,Fe17-,AL,(C) (R=Tb,€Io) ALLOYS. W. B. Yelon, H. Luo, M. Chen (Res. Reactor Ctr., Univ. of Missouri-Columbia, Columbia, MO 6521 1). W. C. Chang, and S .  H. Tsai (Dept. of Phys., Natl. Chung Cheng Univ.. Ming-Hsiung, Chia-Yi, Taiwan, ROC) As part of a comprehensive study on the effect of combined substitutional and interstitial modification on the structure and magnetic propenies of Re,Fe17 compounds, especially with higher substituent concentration, ~ F e 1 7 - , A l , C ,  H~Fe17-,Al, and HqFe17-,AI,C (x= 1-4)  have been studied by using neutron diffraction. All these samples were made by arc melting and were confirmed to have the ThzZn17 type rhombohedral struc- ture (space group R-3m) except for HozFel& HqFel5AI2 which have the Th2Ni17 type hexagonal suucture (space group P63/1t~nc), and H%Fe13A13. a mixture of the two phases with the hexagonal phase domi- nant. The size of the unit cell seems to be the determinant factor in form- ing an ordered rhombohedral phase or a disordered hexagonal phase. Both the substitution of Fe by AI and the insertion of C can lead to the forma- tion of an ordered rhombohedral phase. The site preference of A1 is some- what different with and without C. In the Ho carbided samples, AI prefers the 18h and 18f sites in the rhombohedral structure and tottally avoids the 9d site while in the Ho noncarbided samples, a small amount of AI is found at the hexagonal 6g site which is the cognate of the rhombohedral 9d. In the Tb carbided samples, for AI x=l ,  2 and 3, A1 has a higher occupancy at the 18h site and a much lower one at 6c as compared to Tb2Fe17-,Al,'. At higher Al concentration, AI occupancy at 18h tends to saturate around 40% and the Al site occupancies are similar with and 

Pressure Induced Reversal of the Volume Expansion Caused by Interstitial Nitrogen in Nd₂Fe₁₇N₃

https://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=1378&context=phys_facwork

Pressure Induced Reversal of the Volume Expansion Caused by Interstitial Nitrogen in Nd₂Fe₁₇N₃

Abstract

Similar works

Full text

Available Versions

Missouri University of Science and Technology (Missouri S&T): Scholars' Mine