The scattering factor of C60 molecule have been calculated according toX-ray diffraction theory. By comparing it with the atomic scattering factor of carbon,it is found that the scattering factor of C60 molecule is a ...The scattering factor of C60 molecule have been calculated according toX-ray diffraction theory. By comparing it with the atomic scattering factor of carbon,it is found that the scattering factor of C60 molecule is a sine-oscillating attenuate finction of sinθ/λ depending on the direction of the incident beam, which is attenuatedmore quickly than that of single carbon atom. However, there is nO evident differencefor the different directions when 0.00≤sinθ/λ≤0.15.展开更多
The temperature dependence of thermopower and resistivity for the series of Nd_(0.7)(Ca,Sr,Ba)_(0.3)MnO_(3) with a fixed average A-site cation radius (γA)have been measured.Infrared spectra revealed that the size dif...The temperature dependence of thermopower and resistivity for the series of Nd_(0.7)(Ca,Sr,Ba)_(0.3)MnO_(3) with a fixed average A-site cation radius (γA)have been measured.Infrared spectra revealed that the size differences between various A-site ions cause large local distortions of MnO&octahedra.The thermopower is enhanced above metal-insulator transition temperature Tm and is reduced below T_(m) by increasing amount of A-site cation disorder.The sign change of thermopower induced by A-site cation disorder has been observed at low temperatures.The observed thermopower behaviors have been explained by Mott's formula and the effect of the spin disorder scattering.展开更多
The(001)oriented yttria-stabilized zirconia(YSZ)Hlms with in-plane biaxial texture have been deposited on Si(111)substrates by ion beam assisted deposition at ambient temperature.The effects of ion/atom arrival rate f...The(001)oriented yttria-stabilized zirconia(YSZ)Hlms with in-plane biaxial texture have been deposited on Si(111)substrates by ion beam assisted deposition at ambient temperature.The effects of ion/atom arrival rate fatio(R=(Ar^(+)+O2^(+))/ZrO_(2))and incident angle of bombarding ion beam on the Him texture development were investigated.It was found that the in-plane biaxial texture of the films was improved gradually with increasing ion/atom arrival rate ratio R up to a critical value 1,9,but it was degraded with the further increase of R.The optimal in-plane biaxial texture,whose full width at half maximum of the(111)4>-scan spectrum is 14°,can be obtained at R=1.9 and incident angle of 55°.For a fixed R,the optimal crystallinity and in-plane biaxial alignment of the YSZ Hlms did not appear at the same incident angle and showed an opposite variation with the change of the incident angle from 51°to 55°.C-axis alignment(perpendicular to substrate surface)does not show any substantial variation with the change of incident angle within the range of 47°-56°.展开更多
For a highly oriented Bi_(2)Sr_(2)CaCu_(2)0_(8+y) single crystal with a lower as-grown T_(c)of 72K,on air-annealing at 250℃for 2h,its T_(c)remained unchanged,while increased to 83 K after annealing for 25 h.For anoth...For a highly oriented Bi_(2)Sr_(2)CaCu_(2)0_(8+y) single crystal with a lower as-grown T_(c)of 72K,on air-annealing at 250℃for 2h,its T_(c)remained unchanged,while increased to 83 K after annealing for 25 h.For another crystal with a higher as-grown T_(c)of 86.7K and annealed under the same condition,its T_(c)was unchanged except for a slight improvement ofΔT_(c)and was independent of the annealing time.X-ray diffraction showed that there were no changes of c-axis lattice parameter for the annealed crystals.If the above two crystals,after annealing at 250℃for 25 h,were further annealed at 600℃for 20 h,then T_(c)was increased to the same value of almost 88K and the c-axis lattice parameter showed a dramatic contraction.We suggested that the improvement of superconductivity of the sample annealed at much lower annealing temperature(250℃)are associated with the oxygen diffusion involved in the pervoskite unit and this diffusion from the perovskite unit occurs earlier than that from Bi-O layers.展开更多
Bi_(2)Sr_(2)CaCu_(2)O_(y) single crystals were air-annealed at 300,400,600 and 750℃ for 20h in consequence.Measurements of ac susceptibility and x-ray diffraction showed that at annealing temperature below 400℃,the ...Bi_(2)Sr_(2)CaCu_(2)O_(y) single crystals were air-annealed at 300,400,600 and 750℃ for 20h in consequence.Measurements of ac susceptibility and x-ray diffraction showed that at annealing temperature below 400℃,the change of Tc was dominated by oxygen-diffusion involved in pervoskite unit and was strongly sample-dependent.This diffusion from pervoskite unit occurred earlier than that from Bi-O layers.At annealing temperature over 400℃,with the intercalation of excess oxygen into Bi-O layers,the hole concentration in the crystal was redistributed so that Bi-O reservoir fully determined superconductivity.From the changes of non-uniform strain in annealing process,it was found that structural modification was also closely correlated to superconductivity.展开更多
文摘The scattering factor of C60 molecule have been calculated according toX-ray diffraction theory. By comparing it with the atomic scattering factor of carbon,it is found that the scattering factor of C60 molecule is a sine-oscillating attenuate finction of sinθ/λ depending on the direction of the incident beam, which is attenuatedmore quickly than that of single carbon atom. However, there is nO evident differencefor the different directions when 0.00≤sinθ/λ≤0.15.
基金Supported by the Foundation of the Chinese Academy of Sciences under Grant No.KJ951-A1-401,and the Science Foundation of Anhui Province,China.
文摘The temperature dependence of thermopower and resistivity for the series of Nd_(0.7)(Ca,Sr,Ba)_(0.3)MnO_(3) with a fixed average A-site cation radius (γA)have been measured.Infrared spectra revealed that the size differences between various A-site ions cause large local distortions of MnO&octahedra.The thermopower is enhanced above metal-insulator transition temperature Tm and is reduced below T_(m) by increasing amount of A-site cation disorder.The sign change of thermopower induced by A-site cation disorder has been observed at low temperatures.The observed thermopower behaviors have been explained by Mott's formula and the effect of the spin disorder scattering.
基金Supported by the National Natural Science Foundation of China under Grant No.19875073.
文摘The(001)oriented yttria-stabilized zirconia(YSZ)Hlms with in-plane biaxial texture have been deposited on Si(111)substrates by ion beam assisted deposition at ambient temperature.The effects of ion/atom arrival rate fatio(R=(Ar^(+)+O2^(+))/ZrO_(2))and incident angle of bombarding ion beam on the Him texture development were investigated.It was found that the in-plane biaxial texture of the films was improved gradually with increasing ion/atom arrival rate ratio R up to a critical value 1,9,but it was degraded with the further increase of R.The optimal in-plane biaxial texture,whose full width at half maximum of the(111)4>-scan spectrum is 14°,can be obtained at R=1.9 and incident angle of 55°.For a fixed R,the optimal crystallinity and in-plane biaxial alignment of the YSZ Hlms did not appear at the same incident angle and showed an opposite variation with the change of the incident angle from 51°to 55°.C-axis alignment(perpendicular to substrate surface)does not show any substantial variation with the change of incident angle within the range of 47°-56°.
基金Supported by the National Natural Science Foundation of China under Grant No.59425008the National Center for Research&Development on Superconductivity under Grant No.AJ103.
文摘For a highly oriented Bi_(2)Sr_(2)CaCu_(2)0_(8+y) single crystal with a lower as-grown T_(c)of 72K,on air-annealing at 250℃for 2h,its T_(c)remained unchanged,while increased to 83 K after annealing for 25 h.For another crystal with a higher as-grown T_(c)of 86.7K and annealed under the same condition,its T_(c)was unchanged except for a slight improvement ofΔT_(c)and was independent of the annealing time.X-ray diffraction showed that there were no changes of c-axis lattice parameter for the annealed crystals.If the above two crystals,after annealing at 250℃for 25 h,were further annealed at 600℃for 20 h,then T_(c)was increased to the same value of almost 88K and the c-axis lattice parameter showed a dramatic contraction.We suggested that the improvement of superconductivity of the sample annealed at much lower annealing temperature(250℃)are associated with the oxygen diffusion involved in the pervoskite unit and this diffusion from the perovskite unit occurs earlier than that from Bi-O layers.
基金Supported by the National Natural Science Foundation of China under Grant No.59425008the NationalCenter for Research&Development on Superconductivity under Grant No.AJ103.
文摘Bi_(2)Sr_(2)CaCu_(2)O_(y) single crystals were air-annealed at 300,400,600 and 750℃ for 20h in consequence.Measurements of ac susceptibility and x-ray diffraction showed that at annealing temperature below 400℃,the change of Tc was dominated by oxygen-diffusion involved in pervoskite unit and was strongly sample-dependent.This diffusion from pervoskite unit occurred earlier than that from Bi-O layers.At annealing temperature over 400℃,with the intercalation of excess oxygen into Bi-O layers,the hole concentration in the crystal was redistributed so that Bi-O reservoir fully determined superconductivity.From the changes of non-uniform strain in annealing process,it was found that structural modification was also closely correlated to superconductivity.
