Showing 3 results for Crystal Structure
R. Lotfi Orimi, V. Asghari , M. Lashkarbolouki,
Volume 30, Issue 1 (6-2011)
Abstract
ZnS nanoparticles were synthesized by chemical precipitation method. As-prepared ZnS nanoparticles were found to be stabilized in the form of cubic phase. Cubic to hexagonal structural transformation was studied using X-ray diffraction (XRD). The effect of annealing temperature (100-700 ) on the band gap, particle size, and structural phase was investigated. Photoluminescence studies indicated two strong and narrow emission peaks in blue and orange regions. These two strong and narrow emission peaks were shifted to blue and red regions by increasing the annealing temperature..
F. Nazari, M. Hakimi, H. Mokhtari, A.s. Esmaeily,
Volume 35, Issue 2 (9-2016)
Abstract
In this paper, milling was investigated as a method for production of Mn-Ga binary alloys and the effect of milling process on phase formation of Mn:Ga samples with 2:1 and 3:1 ratio within 1, 2 and 5 hour milling times was studied. For Mn:Ga samples, according to the results, Mn1.86Ga compound with tetragonal structure and I4/mmm space group was a stable phase. Also, some amounts of Mn3Ga compound with orthorhombic structure and Cmca space group was observed in the Mn:Ga solution. The effect of Ge addition, with the purpose of replacing Ge with Ga was also studied in Mn:Ga:Ge (3:0.5:0.5) sample. Although improved magnetic properties is expected with the addition of Ge, but increasing the coercivity was occurred, and saturation magnetization did not change significantly in the studied sample. Ge addition caused elimination of the possibility of formation of asymmetric orthorhombic Mn3Ga phase. In return, two new structures of Mn11Ge8 and MnGaGe were appeared. This phase change was confirmed by studying magnetic behaviour of samples. This behavior can be caused by unbalanced electrostatic forces resulting from Mn-Mn exchange interaction in Mn3Ga orthorhombic structure and substitution of some Ge atoms with Ga.
R. Sobhani, M. Hakimi, M. Khajeh Aminian, P. Kameli,
Volume 35, Issue 3 (12-2016)
Abstract
In this paper, the phase formation process of Mn2.5Ge samples, prepared by mechanical alloying of Mn and Ge metal powders and annealing, has been studied. Results showed that in the milled samples the stable phase is Mn11Ge8 compound with orthorhombic structure and Pnam space group. The value of saturation magnetization increases by increasing milling time from 0.2 up to 1.95 (Am2Kg-1). The remanece of the samples increases by increasing the milling time while the coercivity decreases. Annealing of 15-hour milled sample results in disappearance of Mn and Ge and the formation of new phases of Mn3Ge, Mn5Ge2, Mn5Ge3 and Mn2.3Ge. Mn3Ge is the main phase with Do22 tetragonal structure and I4/mmm space group which is stable and dominant. The enhancement of saturation magnetization in the annealed sample is related to the formation of three new magnetic phases and the increase of coercivity is due to the presence of Mn3Ge compound with tetragonal structure. Studies were replicated on samples made by arc melting method to compare the results and to investigate the effect of the preparation method on phase formation and structural and magnetic properties of the materials. In these samples the saturation value was in range of 0.2 up to 1.95 (Am2Kg-1) depending on preparation methods. Rietveld refinement shows that Mn2.3Ge sample prepared from arc melted under 620oC anealing is single phase. Magnetic analysis of this sample show a saturation magnetization of 5.252(Am2Kg-1) and 0.005 T coercive field.
