The main studying activities and results on space materials science during 1996-1997 in China were summarized. The typical research subjects are crystal growth from melt, crystal growth from solution, nucleation, unde...The main studying activities and results on space materials science during 1996-1997 in China were summarized. The typical research subjects are crystal growth from melt, crystal growth from solution, nucleation, undercooling,solidification of alloys and space experimental hardware. They are carried out by the ground-based studies, the short duration microgravity missions and orbital experiments.展开更多
A transient analysis of Te doped GaSb melt growth process is performed using finite element method.The solute concentration at the growth interface increases with time because of k<1.The growth interface shape beco...A transient analysis of Te doped GaSb melt growth process is performed using finite element method.The solute concentration at the growth interface increases with time because of k<1.The growth interface shape becomes a little flat at the beginning of the growth compared with the initial shape.Radial segregation occurs even under theμg condition.This segregation increases with the increase of gravity when gravity is small,and reaches a maximum at g=10^(-3)for our system.展开更多
The distribution of Ca^(2+)at boundary layer ofα-LiIO3 crystal grown both in space and on earth was studied by the synchrotron x-ray fluorescence microanalysis.It was found that:(1)the Ca^(2+)concentration in the spa...The distribution of Ca^(2+)at boundary layer ofα-LiIO3 crystal grown both in space and on earth was studied by the synchrotron x-ray fluorescence microanalysis.It was found that:(1)the Ca^(2+)concentration in the space-crystal is higher than that in the earth-crystal,(2)a sharp discontinuity of Ca^(2+)concentration is found at boundary layers of space-crystals alone.This finding provides an evidence of microgravity effect on interface structural features in space crystal growth.展开更多
A pseudospin-phonon coupled model in double-time Green's function theory has been developed to investi- gate the dielectric susceptibility of the ferroelectric-dielectric superlattice BaTiO_(3)/SrTiO_(3) (BTO/STO)...A pseudospin-phonon coupled model in double-time Green's function theory has been developed to investi- gate the dielectric susceptibility of the ferroelectric-dielectric superlattice BaTiO_(3)/SrTiO_(3) (BTO/STO). As the pseudospin-pseudospin and pseudospin-phonon interactions increase, the dielectric susceptibility changes from a narrow shape into the strong and broad shape with the peak shifting to a higher temperature region. With increasing pseudospin-phonon interaction in the BTO layer and at smallpseudospin-pseudospin interaction in BTO layer, the dielectric susceptibility was sensitively adjusted around the transition temperature of strontium titanate, and at large pseudospin-pseudospin interaction in the BTO layer, the dielectric susceptibility was increased in the high-temperature region covering the tetragonal-cubic transition temperature of barium titanate. A critical period of 10/I0 in the BTO/STO superlattice has been obtained, which is in good agreement with the experimental data of 40A, for ten unit cells.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
Photoinduced light scattering of Co-and Cr-doped lithium niobate crystals is examined.The light climbing effect is observed in the Co-and Cr-doped lithium niobate crystals.The influences of the incident light waveleng...Photoinduced light scattering of Co-and Cr-doped lithium niobate crystals is examined.The light climbing effect is observed in the Co-and Cr-doped lithium niobate crystals.The influences of the incident light wavelength,laser power,sample thickness and doping effects on the light climbing effect are studied.Higher photodamage threshold and quicker light climbing are found in the Cr-and Co-doped lithium niobate,which are attributed to the higher space electrical charge field and both different valence and occupation of the doping ions,respectively.展开更多
文摘The main studying activities and results on space materials science during 1996-1997 in China were summarized. The typical research subjects are crystal growth from melt, crystal growth from solution, nucleation, undercooling,solidification of alloys and space experimental hardware. They are carried out by the ground-based studies, the short duration microgravity missions and orbital experiments.
基金Supported by the Climbing Project of the National Ministry of Science and Technology(95-Yu-34)and the Foundation of National Ministry of Education.
文摘A transient analysis of Te doped GaSb melt growth process is performed using finite element method.The solute concentration at the growth interface increases with time because of k<1.The growth interface shape becomes a little flat at the beginning of the growth compared with the initial shape.Radial segregation occurs even under theμg condition.This segregation increases with the increase of gravity when gravity is small,and reaches a maximum at g=10^(-3)for our system.
文摘The distribution of Ca^(2+)at boundary layer ofα-LiIO3 crystal grown both in space and on earth was studied by the synchrotron x-ray fluorescence microanalysis.It was found that:(1)the Ca^(2+)concentration in the space-crystal is higher than that in the earth-crystal,(2)a sharp discontinuity of Ca^(2+)concentration is found at boundary layers of space-crystals alone.This finding provides an evidence of microgravity effect on interface structural features in space crystal growth.
基金Supported by the Climbing Project of National Commission of Science and Technology.
文摘A pseudospin-phonon coupled model in double-time Green's function theory has been developed to investi- gate the dielectric susceptibility of the ferroelectric-dielectric superlattice BaTiO_(3)/SrTiO_(3) (BTO/STO). As the pseudospin-pseudospin and pseudospin-phonon interactions increase, the dielectric susceptibility changes from a narrow shape into the strong and broad shape with the peak shifting to a higher temperature region. With increasing pseudospin-phonon interaction in the BTO layer and at smallpseudospin-pseudospin interaction in BTO layer, the dielectric susceptibility was sensitively adjusted around the transition temperature of strontium titanate, and at large pseudospin-pseudospin interaction in the BTO layer, the dielectric susceptibility was increased in the high-temperature region covering the tetragonal-cubic transition temperature of barium titanate. A critical period of 10/I0 in the BTO/STO superlattice has been obtained, which is in good agreement with the experimental data of 40A, for ten unit cells.
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 Climbing Program of National Commit tee of Science and Technology of China,。
文摘Photoinduced light scattering of Co-and Cr-doped lithium niobate crystals is examined.The light climbing effect is observed in the Co-and Cr-doped lithium niobate crystals.The influences of the incident light wavelength,laser power,sample thickness and doping effects on the light climbing effect are studied.Higher photodamage threshold and quicker light climbing are found in the Cr-and Co-doped lithium niobate,which are attributed to the higher space electrical charge field and both different valence and occupation of the doping ions,respectively.
