The structure of bcc-Fe80Cu20 solid solution produced by mechanical alloying of the elemental bcc-Fe and fcc-Cu powders has been studied using X-ray diffraction and the extended X-ray absorption fine structure (EXAFS)...The structure of bcc-Fe80Cu20 solid solution produced by mechanical alloying of the elemental bcc-Fe and fcc-Cu powders has been studied using X-ray diffraction and the extended X-ray absorption fine structure (EXAFS) techniques. The disappearance of elemental Fe and Cu X-ray diffraction (XRD) peaks and the presence of bcc structural XRD peaks illustrate the formation of a nanocrystalline single-phase bcc-Fe80Cu20 solid solution. From the EXAFS result, the clear observation of Cu atoms taking on bcc coordination in the solid solution and Fe atoms remaining bcc structure further verifies the reality of atomic alloying between Fe and Cu atoms and the lattice change of Cu from fcc to bcc. However, the supersaturated bcc solid solution is not chemically uniform, i.e., some regions are rich in Fe atoms and other regions rich in Cu atoms.展开更多
The crystal structure of new compound Ba 3BPO 7 has been solved by X ray powder diffraction technique. As a new structure type, the positions of barium, boron and phosphate atoms have been determined by single crystal...The crystal structure of new compound Ba 3BPO 7 has been solved by X ray powder diffraction technique. As a new structure type, the positions of barium, boron and phosphate atoms have been determined by single crystal direct method after profile decomposition from Ba 3BPO 7 X ray powder diffraction patterns. The positions of oxygen atoms have been determined by the interpretation of their vibration spectra which indicate that in this crystal the boron and phosphorus atoms form BO 3 and PO 4 polyhedra. The structure has been refined by Rietveld technique based on the above model.展开更多
New oxometallides with the formula Ba5Y8-xMn4021-1.5x （x = 0, 1） are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 （Y8） and 5/7/4 （Y7）...New oxometallides with the formula Ba5Y8-xMn4021-1.5x （x = 0, 1） are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 （Y8） and 5/7/4 （Y7） are obtained. The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction, magnetization, conductivity, and dielectricity measurements. The Ba5Y8-xMn4021-1.5x compound is demonstrated to be a Y-deficient solid solution. The solid solution compound Ba5Y8-xMn4021-1.5x crystallizes into tetragonal symmetry with the space group I4/m. Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y（2） site. Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds, and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples, respectively. Strong frequency dependences of the dielectric constant are observed above -175 K for the two compounds.展开更多
Ce Zr O solid solution was prepared by four different methods, i.e., decomposition of nitrate, coprecipiation, hydroxysuainic acid sol gel as well as citrate sol gel, and characterized by using X ray powder diffr...Ce Zr O solid solution was prepared by four different methods, i.e., decomposition of nitrate, coprecipiation, hydroxysuainic acid sol gel as well as citrate sol gel, and characterized by using X ray powder diffraction, Raman and temperature programmed reduction. The phase composition and the reduction properties of Ce Zr O depend on the preparation method. A cubic Ce 0.5 Zr 0.5 O 2 solid solution can be obtained by using the sol gel method. The Ce Zr O solid solution prepared by using decomposition or coprecipiation was composed of cubic Ce 0.8 Zr 0.2 O 2 and tetragonal Ce 0.2 Zr 0.8 O 2 solid solution. The Ce Zr O solid solution prepared with different methods shows the different reduction properties owing to different phase composition. Results of differential thermal analysis and XRD show that Ce 0.5 Zr 0.5 O 2 solid solution is formed during the decomposition or combustion of the gel.展开更多
Microstructural change of YBaCuO film/YSZ substrate with and without proton irradiation has been studied by scanning electron microscope and X- ray diffraction techniques. Structural analysis has shown that conversion...Microstructural change of YBaCuO film/YSZ substrate with and without proton irradiation has been studied by scanning electron microscope and X- ray diffraction techniques. Structural analysis has shown that conversion from tetragonal to orthorhombic phases, reduction of nonsuperconducting phase and preferential rearrangement of crystal grains are all favorable to the improvement of superconductivity in the YBaCuO film supported by YSZ substrate by proton beam bombardment.展开更多
The 500℃ isothermal section of the phase diagram of the Cu Be Ag (Cu≥50 at%) ternary system was investigated by X ray powder diffraction. The isothermal section consists of two single phase regions (namely α C...The 500℃ isothermal section of the phase diagram of the Cu Be Ag (Cu≥50 at%) ternary system was investigated by X ray powder diffraction. The isothermal section consists of two single phase regions (namely α Cu and CuBe), two two phase regions (namely α Cu+Ag and CuBe+α Cu) and one three phase region (namely α Cu+Ag+CuBe). The maximum solubility of Be in α Cu and Ag in α Cu are about 6.6 at% and 0.8 at% respectively.展开更多
基金Natural Science Foundation of Guangdong Province (Grant No. 20010056).
文摘The structure of bcc-Fe80Cu20 solid solution produced by mechanical alloying of the elemental bcc-Fe and fcc-Cu powders has been studied using X-ray diffraction and the extended X-ray absorption fine structure (EXAFS) techniques. The disappearance of elemental Fe and Cu X-ray diffraction (XRD) peaks and the presence of bcc structural XRD peaks illustrate the formation of a nanocrystalline single-phase bcc-Fe80Cu20 solid solution. From the EXAFS result, the clear observation of Cu atoms taking on bcc coordination in the solid solution and Fe atoms remaining bcc structure further verifies the reality of atomic alloying between Fe and Cu atoms and the lattice change of Cu from fcc to bcc. However, the supersaturated bcc solid solution is not chemically uniform, i.e., some regions are rich in Fe atoms and other regions rich in Cu atoms.
文摘The crystal structure of new compound Ba 3BPO 7 has been solved by X ray powder diffraction technique. As a new structure type, the positions of barium, boron and phosphate atoms have been determined by single crystal direct method after profile decomposition from Ba 3BPO 7 X ray powder diffraction patterns. The positions of oxygen atoms have been determined by the interpretation of their vibration spectra which indicate that in this crystal the boron and phosphorus atoms form BO 3 and PO 4 polyhedra. The structure has been refined by Rietveld technique based on the above model.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50872148 and 51072225)the National Basic Research Program of China (Grant No. 2007CB925003)
文摘New oxometallides with the formula Ba5Y8-xMn4021-1.5x （x = 0, 1） are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 （Y8） and 5/7/4 （Y7） are obtained. The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction, magnetization, conductivity, and dielectricity measurements. The Ba5Y8-xMn4021-1.5x compound is demonstrated to be a Y-deficient solid solution. The solid solution compound Ba5Y8-xMn4021-1.5x crystallizes into tetragonal symmetry with the space group I4/m. Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y（2） site. Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds, and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples, respectively. Strong frequency dependences of the dielectric constant are observed above -175 K for the two compounds.
文摘Ce Zr O solid solution was prepared by four different methods, i.e., decomposition of nitrate, coprecipiation, hydroxysuainic acid sol gel as well as citrate sol gel, and characterized by using X ray powder diffraction, Raman and temperature programmed reduction. The phase composition and the reduction properties of Ce Zr O depend on the preparation method. A cubic Ce 0.5 Zr 0.5 O 2 solid solution can be obtained by using the sol gel method. The Ce Zr O solid solution prepared by using decomposition or coprecipiation was composed of cubic Ce 0.8 Zr 0.2 O 2 and tetragonal Ce 0.2 Zr 0.8 O 2 solid solution. The Ce Zr O solid solution prepared with different methods shows the different reduction properties owing to different phase composition. Results of differential thermal analysis and XRD show that Ce 0.5 Zr 0.5 O 2 solid solution is formed during the decomposition or combustion of the gel.
文摘Microstructural change of YBaCuO film/YSZ substrate with and without proton irradiation has been studied by scanning electron microscope and X- ray diffraction techniques. Structural analysis has shown that conversion from tetragonal to orthorhombic phases, reduction of nonsuperconducting phase and preferential rearrangement of crystal grains are all favorable to the improvement of superconductivity in the YBaCuO film supported by YSZ substrate by proton beam bombardment.
文摘The 500℃ isothermal section of the phase diagram of the Cu Be Ag (Cu≥50 at%) ternary system was investigated by X ray powder diffraction. The isothermal section consists of two single phase regions (namely α Cu and CuBe), two two phase regions (namely α Cu+Ag and CuBe+α Cu) and one three phase region (namely α Cu+Ag+CuBe). The maximum solubility of Be in α Cu and Ag in α Cu are about 6.6 at% and 0.8 at% respectively.
