High pure wurtzite structure GaN has been synthesized by gas reaction method.Its structure was determined by powder x-ray diffraction using the Rietveld technique.The heat capacity Cp was measured from 113 to 1073 K,w...High pure wurtzite structure GaN has been synthesized by gas reaction method.Its structure was determined by powder x-ray diffraction using the Rietveld technique.The heat capacity Cp was measured from 113 to 1073 K,which can be represented by Cp=0.362+3.010 × 10^(-4)T-3.411 × 10^(3)T-2-7.791 × 10^(-8)T^(2).No measurable phase transition was observed in this temperature range.展开更多
A series of crystals of Ba_(x)Sr_(1-x)(NO_(3))_(2) (x=0-0.98) were grown from aqueous solutions by the evaporation method and characterized by x-ray powder diffraction and high resolution x-ray diffraction. All diffra...A series of crystals of Ba_(x)Sr_(1-x)(NO_(3))_(2) (x=0-0.98) were grown from aqueous solutions by the evaporation method and characterized by x-ray powder diffraction and high resolution x-ray diffraction. All diffraction data are well indexed according to simple cubic structure. The variation of lattice constants with the concentrations of Ba^(2+) in the crystals accorded quite well to the Vegard's Law. The results of high-resolution x-ray diffraction show that the crystalline quality of Ba_(x)Sr_(1-x)(NO_(3))_(2) decreases with x increasing. The distribution of Ba^(2+) between the solution and solid phase indicated that Ba^(2+) is enriched in the solid phase. It could be attributed to the solubility of Ba(NO3)2 in water being less than that of Sr(NO_(3))_(2).展开更多
The magnetoresistance(MR)behavior of La_((2-x)/3)Bi_(x/3)Ca_(l/3)MnO_(3)(x=0.4)compound was investigated.The compound exhibits complex magnetic transitions,i.e.,paramagnetic-canted ferromagnetic-ferromagnetic-spin gla...The magnetoresistance(MR)behavior of La_((2-x)/3)Bi_(x/3)Ca_(l/3)MnO_(3)(x=0.4)compound was investigated.The compound exhibits complex magnetic transitions,i.e.,paramagnetic-canted ferromagnetic-ferromagnetic-spin glass transitions.The temperature dependence of resistivity of the compound indicates a semiconducting behavior,and no semiconductor-metal transition was associated with these magnetic transitions.The magnetoresistance ratio exhibits a critical maximum corresponding to the canted ferromagnetic transition.A MR ratio as large as 86%was observed at 85 K.The temperature dependence of MR ratio is well described by the relation of(ρo-ρH)/ρo=A(M/M_(s))^(2).展开更多
基金Supported by the Chinese Academy of Sciences under Contract No.KJ952-J1-411.
文摘High pure wurtzite structure GaN has been synthesized by gas reaction method.Its structure was determined by powder x-ray diffraction using the Rietveld technique.The heat capacity Cp was measured from 113 to 1073 K,which can be represented by Cp=0.362+3.010 × 10^(-4)T-3.411 × 10^(3)T-2-7.791 × 10^(-8)T^(2).No measurable phase transition was observed in this temperature range.
基金Supported by the Climbing Project of National Commission of Science and Technology(95-Yu-34).
文摘A series of crystals of Ba_(x)Sr_(1-x)(NO_(3))_(2) (x=0-0.98) were grown from aqueous solutions by the evaporation method and characterized by x-ray powder diffraction and high resolution x-ray diffraction. All diffraction data are well indexed according to simple cubic structure. The variation of lattice constants with the concentrations of Ba^(2+) in the crystals accorded quite well to the Vegard's Law. The results of high-resolution x-ray diffraction show that the crystalline quality of Ba_(x)Sr_(1-x)(NO_(3))_(2) decreases with x increasing. The distribution of Ba^(2+) between the solution and solid phase indicated that Ba^(2+) is enriched in the solid phase. It could be attributed to the solubility of Ba(NO3)2 in water being less than that of Sr(NO_(3))_(2).
基金Supported by the National Natural Science Foundation of China under Grant No.29401006.
文摘The magnetoresistance(MR)behavior of La_((2-x)/3)Bi_(x/3)Ca_(l/3)MnO_(3)(x=0.4)compound was investigated.The compound exhibits complex magnetic transitions,i.e.,paramagnetic-canted ferromagnetic-ferromagnetic-spin glass transitions.The temperature dependence of resistivity of the compound indicates a semiconducting behavior,and no semiconductor-metal transition was associated with these magnetic transitions.The magnetoresistance ratio exhibits a critical maximum corresponding to the canted ferromagnetic transition.A MR ratio as large as 86%was observed at 85 K.The temperature dependence of MR ratio is well described by the relation of(ρo-ρH)/ρo=A(M/M_(s))^(2).
