The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72- Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry ...The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72- Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd5Si1.72Ge2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (TC) of the compounds. The magnetic entropy change of (Gd1-xTbx)5Si1.72Ge2.28 alloys retains a large value in the low magnetic field of 1.0 T. The maximum magnetic entropy change for (Gd0.80Tb0.20)5Si1.72Ge2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K), which is nearly 4 times as large as that of (Gd0.3Dy0.7)5Si4 compound (|-Smax| = 2.24 J/(kg·K), T_C = 198 K).展开更多
The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Pow-der XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1 h had a significant magn...The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Pow-der XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1 h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J·kg?1·K?1 under a magnetic field change of 0―5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment.展开更多
The magnetic phase transition and magneto- caloric effect of Gd5Si1.85Ge2.15 alloy are studied. The alloy was prepared from distilled commercial gadolinium. The major impurities (in wt.%) in the distilled commercial G...The magnetic phase transition and magneto- caloric effect of Gd5Si1.85Ge2.15 alloy are studied. The alloy was prepared from distilled commercial gadolinium. The major impurities (in wt.%) in the distilled commercial Gd are 0.016 O, 0.0054 C, and 0.0016 N. The impurities are higher than those in the high pure Gd but lower than those in commercial Gd. The results of X-ray diffraction and magnetic susceptibility show that there exists the first-order magnetic phase transition in the Gd5Si1.85Ge2.15 alloy at 253 K. The maximum of magnetic entropy change Smax is 12.5 J/kg·K near the temperature of magnetic phase transition in the alloy.展开更多
基金Project (50371058) supported by the National Natural Science Foundation of China
文摘The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72- Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd5Si1.72Ge2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (TC) of the compounds. The magnetic entropy change of (Gd1-xTbx)5Si1.72Ge2.28 alloys retains a large value in the low magnetic field of 1.0 T. The maximum magnetic entropy change for (Gd0.80Tb0.20)5Si1.72Ge2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K), which is nearly 4 times as large as that of (Gd0.3Dy0.7)5Si4 compound (|-Smax| = 2.24 J/(kg·K), T_C = 198 K).
基金This work was supported by the National High Technology Research and Development Program of China(No.2002AA324010).
文摘The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Pow-der XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1 h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J·kg?1·K?1 under a magnetic field change of 0―5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment.
基金supported by the National Natural Science Foundation of China(Grant No.50071006)the“863”Program(Grant No.2002AA324101).
文摘The magnetic phase transition and magneto- caloric effect of Gd5Si1.85Ge2.15 alloy are studied. The alloy was prepared from distilled commercial gadolinium. The major impurities (in wt.%) in the distilled commercial Gd are 0.016 O, 0.0054 C, and 0.0016 N. The impurities are higher than those in the high pure Gd but lower than those in commercial Gd. The results of X-ray diffraction and magnetic susceptibility show that there exists the first-order magnetic phase transition in the Gd5Si1.85Ge2.15 alloy at 253 K. The maximum of magnetic entropy change Smax is 12.5 J/kg·K near the temperature of magnetic phase transition in the alloy.
