The solid state solutions of europium transition element oxides Eu (Fe0.8M0.2)O3 (M=Sc, Cr, Mn, Co) are synthesized. The X-ray diffraction of the compound shows that all the compounds possess the perovskite structures...The solid state solutions of europium transition element oxides Eu (Fe0.8M0.2)O3 (M=Sc, Cr, Mn, Co) are synthesized. The X-ray diffraction of the compound shows that all the compounds possess the perovskite structures. Both the 151Eu Mossbauer spectra and the Fe Mossbauer spectra are measured. The hyperfine magnetic field and non-axisymmetric electric field gradient are observed in the Eu Mossbauer spectrum. The 57Fe Mossbauer spectrum shows that there are four components of hyperfine fields corresponding to four kinds of different neighbours of the Fe ion.展开更多
采用机械合金化法制备Al V Fe纳米粉末 ,通过测定M ssbauer效应 ,研究了不同球磨能量对制备Al V Fe纳米粉末的影响·结果表明 ,振动球磨与高能球磨所制备的Al V Fe纳米粉末结构均由非晶和α Al纳米晶组成 ,其非晶含量随着球磨能量...采用机械合金化法制备Al V Fe纳米粉末 ,通过测定M ssbauer效应 ,研究了不同球磨能量对制备Al V Fe纳米粉末的影响·结果表明 ,振动球磨与高能球磨所制备的Al V Fe纳米粉末结构均由非晶和α Al纳米晶组成 ,其非晶含量随着球磨能量的增加而有所不同·展开更多
The aim of the present paper was to study the large magnetocaloric effect observed in LaFe_(11.35)Co_(0.6)Si_(1.05)alloy. X-ray diffraction(XRD) result reveals a coexistence of two crystalline phases: a dominant La(Fe...The aim of the present paper was to study the large magnetocaloric effect observed in LaFe_(11.35)Co_(0.6)Si_(1.05)alloy. X-ray diffraction(XRD) result reveals a coexistence of two crystalline phases: a dominant La(Fe,Si)_(13)-type and a minor a-Fe(Co,Si). It is confirmed by the Mössbauer spectroscopy and microstructural observations accompanied by an energy-dispersive spectroscopy(EDS) analysis. The value of the magnetic entropy changes(|S_(M)|) in the vicinity of the Curie temperature(TC= 268 K) was calculated using thermomagnetic Maxwell relation, and it equals to 21.4 J·kg^(-1)·K^(-1) under the change in an external magnetic field of μ_(0)ΔH = 3T. The investigation of magnetic phase transition was carried out using the Landau theory, an analysis of the field dependences of the magnetic entropy change and universal scaling curve, revealing the second order of phase transition in the studied material.展开更多
In this paper, we performed calculations to investigate the dielectric, piezoelectric properties, Born effective charge （BEC）, and spontaneous polarization of Sr2M207, the method used in our study was a well-known d...In this paper, we performed calculations to investigate the dielectric, piezoelectric properties, Born effective charge （BEC）, and spontaneous polarization of Sr2M207, the method used in our study was a well-known density functional theory based on first-principles. The optimized results were in good agreement with previous experiments and calculations. which indicates that our calculated method is reasonable. The research we have done suggested that greater piezoelectric components of Sr2Nb207 were e31 and e33, and the contributions were derived from the A I. By studying the Born effective charge, it could be seen that the valence of ions changed, and the O of Sr2Nb207 were most obviously that caused by the covalent character of ions and the hybridization of O-2p and Nb-4d. The spontaneous polarization of Sr2Nb2O7 in the [001 ] direction is 25 p_C/cm2, while for Sr2Ta2O7, there was no spontaneous polarization in the paraelectric state. Finally, the effect of pressure on the piezoelectric properties were also investigated, the polarization of Sr2Nb2O7 decreased linearly with the increase alter pressure. All our preliminary results throw light on the nature of dielectric, piezoelectric properties, Born effective charge, and spontaneous polarization of Sr2M2OT, it was helpful for experimental research, the development of new materials, and future applications.展开更多
Six amorphous alloys (Alloy 1: Fe<sub>56</sub>Co<sub>24</sub>Nb<sub>4</sub>B<sub>13</sub>Si<sub>2</sub>Cu<sub>1</sub>, Alloy 2: Fe<sub>68.5...Six amorphous alloys (Alloy 1: Fe<sub>56</sub>Co<sub>24</sub>Nb<sub>4</sub>B<sub>13</sub>Si<sub>2</sub>Cu<sub>1</sub>, Alloy 2: Fe<sub>68.5</sub>Co<sub>5</sub>Nb<sub>3</sub>Cu<sub>1</sub>Si<sub>15.5</sub>B<sub>7</sub>, Alloy 3: Fe<sub>75.3</sub>Ni<sub>0.8</sub>Cr<sub>0.9</sub>Si<sub>8.7</sub>B<sub>14.3</sub>, Alloy 4: Fe<sub>56</sub>Co<sub>24</sub>Cr<sub>10</sub>Nb<sub>4</sub>B<sub>3</sub>Si<sub>1</sub>Cu<sub>2</sub>, Alloy 5: Fe<sub>72.9</sub>Nb<sub>3</sub>Cu<sub>1</sub>Si<sub>16.2</sub>B<sub>6.9</sub>, Alloy 6: Fe<sub>83.3</sub>Si<sub>8.6</sub>Nb<sub>5.5</sub>B<sub>1.4</sub>Cu<sub>1.2</sub>) were selected in terms of their composition and magnetostriction constants and uniformly irradiated in a high radiation environment in Hall A of the Thomas Jefferson National Accelerator Facility. The 2 GeV electron beam irradiation-induced effects were characterized by Mӧssbauer spectroscopy. The microstructural changes were related to the evolution of the hyperfine magnetic field distributions and isomer shifts. In particular, the occurrence of stress centers in the amorphous materials was evidenced.展开更多
Solid solution of spinel ferrite Cu1-xZnxFe2-yGayO4 with (0.0≤x≤0.5 and y=0.1) are synthesized. XRD measurements confirm the presence of single-phase tetragonal structure with c/a>1 for CuFe2O4 and samples with (...Solid solution of spinel ferrite Cu1-xZnxFe2-yGayO4 with (0.0≤x≤0.5 and y=0.1) are synthesized. XRD measurements confirm the presence of single-phase tetragonal structure with c/a>1 for CuFe2O4 and samples with (x=0.0 and 0.1). The tetragonal phase is attributed to the presence of the cooperative Jahn-Teller Cu ions in the octahedral B-site in the spinel lattice. Tetragonal-to-cubic transformation is occurred at the compositional parameter x≥0.2 and the lattice parameter a is found to decrease with increasing Zn content x. 57Fe Mssbauer measurements at 293K for these compounds reveal superparamagnetic phase for samples with (0.0≤x≤0.2). In contrast,Mssbauer spectra at 12K for these materials show well ordered spectra where,the cation distribution and the hyperfine parameters are determined.展开更多
文摘The solid state solutions of europium transition element oxides Eu (Fe0.8M0.2)O3 (M=Sc, Cr, Mn, Co) are synthesized. The X-ray diffraction of the compound shows that all the compounds possess the perovskite structures. Both the 151Eu Mossbauer spectra and the Fe Mossbauer spectra are measured. The hyperfine magnetic field and non-axisymmetric electric field gradient are observed in the Eu Mossbauer spectrum. The 57Fe Mossbauer spectrum shows that there are four components of hyperfine fields corresponding to four kinds of different neighbours of the Fe ion.
文摘The aim of the present paper was to study the large magnetocaloric effect observed in LaFe_(11.35)Co_(0.6)Si_(1.05)alloy. X-ray diffraction(XRD) result reveals a coexistence of two crystalline phases: a dominant La(Fe,Si)_(13)-type and a minor a-Fe(Co,Si). It is confirmed by the Mössbauer spectroscopy and microstructural observations accompanied by an energy-dispersive spectroscopy(EDS) analysis. The value of the magnetic entropy changes(|S_(M)|) in the vicinity of the Curie temperature(TC= 268 K) was calculated using thermomagnetic Maxwell relation, and it equals to 21.4 J·kg^(-1)·K^(-1) under the change in an external magnetic field of μ_(0)ΔH = 3T. The investigation of magnetic phase transition was carried out using the Landau theory, an analysis of the field dependences of the magnetic entropy change and universal scaling curve, revealing the second order of phase transition in the studied material.
基金Project supported by the National Natural Science Foundation of China(Grant No.51672220)the 111 Program of the Ministry of Education of China(Grant No.B08040)+3 种基金the National Defense Science Foundation(Grant No.32102060303)the Xi’an Science and Technology Foundationthe Shaanxi Provincial Science Foundationthe Gaofeng Project of Northwestern Polytechnical University,China(Grant No.17GH020824)
文摘In this paper, we performed calculations to investigate the dielectric, piezoelectric properties, Born effective charge （BEC）, and spontaneous polarization of Sr2M207, the method used in our study was a well-known density functional theory based on first-principles. The optimized results were in good agreement with previous experiments and calculations. which indicates that our calculated method is reasonable. The research we have done suggested that greater piezoelectric components of Sr2Nb207 were e31 and e33, and the contributions were derived from the A I. By studying the Born effective charge, it could be seen that the valence of ions changed, and the O of Sr2Nb207 were most obviously that caused by the covalent character of ions and the hybridization of O-2p and Nb-4d. The spontaneous polarization of Sr2Nb2O7 in the [001 ] direction is 25 p_C/cm2, while for Sr2Ta2O7, there was no spontaneous polarization in the paraelectric state. Finally, the effect of pressure on the piezoelectric properties were also investigated, the polarization of Sr2Nb2O7 decreased linearly with the increase alter pressure. All our preliminary results throw light on the nature of dielectric, piezoelectric properties, Born effective charge, and spontaneous polarization of Sr2M2OT, it was helpful for experimental research, the development of new materials, and future applications.
文摘Six amorphous alloys (Alloy 1: Fe<sub>56</sub>Co<sub>24</sub>Nb<sub>4</sub>B<sub>13</sub>Si<sub>2</sub>Cu<sub>1</sub>, Alloy 2: Fe<sub>68.5</sub>Co<sub>5</sub>Nb<sub>3</sub>Cu<sub>1</sub>Si<sub>15.5</sub>B<sub>7</sub>, Alloy 3: Fe<sub>75.3</sub>Ni<sub>0.8</sub>Cr<sub>0.9</sub>Si<sub>8.7</sub>B<sub>14.3</sub>, Alloy 4: Fe<sub>56</sub>Co<sub>24</sub>Cr<sub>10</sub>Nb<sub>4</sub>B<sub>3</sub>Si<sub>1</sub>Cu<sub>2</sub>, Alloy 5: Fe<sub>72.9</sub>Nb<sub>3</sub>Cu<sub>1</sub>Si<sub>16.2</sub>B<sub>6.9</sub>, Alloy 6: Fe<sub>83.3</sub>Si<sub>8.6</sub>Nb<sub>5.5</sub>B<sub>1.4</sub>Cu<sub>1.2</sub>) were selected in terms of their composition and magnetostriction constants and uniformly irradiated in a high radiation environment in Hall A of the Thomas Jefferson National Accelerator Facility. The 2 GeV electron beam irradiation-induced effects were characterized by Mӧssbauer spectroscopy. The microstructural changes were related to the evolution of the hyperfine magnetic field distributions and isomer shifts. In particular, the occurrence of stress centers in the amorphous materials was evidenced.
文摘Solid solution of spinel ferrite Cu1-xZnxFe2-yGayO4 with (0.0≤x≤0.5 and y=0.1) are synthesized. XRD measurements confirm the presence of single-phase tetragonal structure with c/a>1 for CuFe2O4 and samples with (x=0.0 and 0.1). The tetragonal phase is attributed to the presence of the cooperative Jahn-Teller Cu ions in the octahedral B-site in the spinel lattice. Tetragonal-to-cubic transformation is occurred at the compositional parameter x≥0.2 and the lattice parameter a is found to decrease with increasing Zn content x. 57Fe Mssbauer measurements at 293K for these compounds reveal superparamagnetic phase for samples with (0.0≤x≤0.2). In contrast,Mssbauer spectra at 12K for these materials show well ordered spectra where,the cation distribution and the hyperfine parameters are determined.
