A combined study examining the temperature dependencies of Raman scattering and photoluminescence(PL)of a YBa2 Cu3 O7(YBCO)matrix doped with SiO2(12 nm;0.01 wt%.,0.10 wt%)and Zn0.95Mn0.05O(20 nm;0.02 wt%,0.10 wt%)nano...A combined study examining the temperature dependencies of Raman scattering and photoluminescence(PL)of a YBa2 Cu3 O7(YBCO)matrix doped with SiO2(12 nm;0.01 wt%.,0.10 wt%)and Zn0.95Mn0.05O(20 nm;0.02 wt%,0.10 wt%)nanoparticles was presented.X-ray diffraction(XRD)analysis confirms that both YBCO types exhibit aperovskite structure with the orthorhombic Pmmm phase.The microstructure was examined using environmental scanning electron microscopy(ESEM).Raman scattering and photoluminescence measurements as functions of temperature were conducted in the 77-837 K range.The photoluminescence intensity is observed to decrease for the doped YBCO than for the pure YBCO,because of localized defects.The photoluminescence spectrum is primarily composed of three bands at 1.60,1.88,and 2.40 eV.A clearly pronounced correlation is observed between electronic and structural changes in the doped YBCO,which is due to the temperature,illumination,added oxygen or metal ions,and spectral parameters.The PL integrated intensity as a function of the inverse temperature was simulated using the Arrhenius model.This analysis reveals that the energy exchange between the different levels in the pure and doped YBCO was conducted via two vibration modes only,which are strongly linked to the oxygen and copper atoms in the YBCO matrix.The temperature dependencies of the modes at 340 and 500 cm-1 exhibit softening with temperature increase,resulting from microstructure control,which may be due to small concentrations of Si,Zn,and Mn substitutions at the chain Cu(1)and plane Cu(2)sites.展开更多
The dependence of the effective penetration depthλe,on the external magnetic field in a high-Tc superconducter YBa2Cu3O7 has been measured by both dc and ac methods at liquid-nigtrogen temperature.It is found,thatλe...The dependence of the effective penetration depthλe,on the external magnetic field in a high-Tc superconducter YBa2Cu3O7 has been measured by both dc and ac methods at liquid-nigtrogen temperature.It is found,thatλe increases rapidly with increasing external field and is 0.13~0.15mm in macroscopic scale.The Hcl of the specimen,about 800e at 77K here,can be determined more reliably by comparing dcλe with acλe.The difference betweenλedc andλeac,and the jumping ofλedc may indicate the characters of superconducting glass.展开更多
We fabricated YBa2Cu3O7–d bulk ceramics with a domestic microwave oven and investigated the effect of pressure at the press procedure. If the pressure was not high enough, the ratio of BaCuO2 phase became large, esti...We fabricated YBa2Cu3O7–d bulk ceramics with a domestic microwave oven and investigated the effect of pressure at the press procedure. If the pressure was not high enough, the ratio of BaCuO2 phase became large, estimated from x-ray diffraction (XRD) measurements. We found that the pressure should be 700 kgf/cm2 at least in order to suppress the BaCuO2 phase.展开更多
YBa2Cu3Ox(YBCO) thin films grown on different substrates with and/or without Eu2CuO4(ECO) buffer layer were investigated by X-ray wide angle diffraction,reflection,diffuse scattering and topography.Theresults show tha...YBa2Cu3Ox(YBCO) thin films grown on different substrates with and/or without Eu2CuO4(ECO) buffer layer were investigated by X-ray wide angle diffraction,reflection,diffuse scattering and topography.Theresults show that for the yttria stabilized ZrO2(YSZ) substrate,the presence of an ECO buffer layer improves the crystalline quality of the YBCO film,while a negative effect is observed for the SrTiO3(STO) substrate.The lateral correlation length for a sample grown on a YSZ substrate with ECO buffer Layer is much greater than grown on an STO subetrate.The STO substrate used has mosaic structure.2001 Elsevier Science B.V.All rights reserved.展开更多
文摘A combined study examining the temperature dependencies of Raman scattering and photoluminescence(PL)of a YBa2 Cu3 O7(YBCO)matrix doped with SiO2(12 nm;0.01 wt%.,0.10 wt%)and Zn0.95Mn0.05O(20 nm;0.02 wt%,0.10 wt%)nanoparticles was presented.X-ray diffraction(XRD)analysis confirms that both YBCO types exhibit aperovskite structure with the orthorhombic Pmmm phase.The microstructure was examined using environmental scanning electron microscopy(ESEM).Raman scattering and photoluminescence measurements as functions of temperature were conducted in the 77-837 K range.The photoluminescence intensity is observed to decrease for the doped YBCO than for the pure YBCO,because of localized defects.The photoluminescence spectrum is primarily composed of three bands at 1.60,1.88,and 2.40 eV.A clearly pronounced correlation is observed between electronic and structural changes in the doped YBCO,which is due to the temperature,illumination,added oxygen or metal ions,and spectral parameters.The PL integrated intensity as a function of the inverse temperature was simulated using the Arrhenius model.This analysis reveals that the energy exchange between the different levels in the pure and doped YBCO was conducted via two vibration modes only,which are strongly linked to the oxygen and copper atoms in the YBCO matrix.The temperature dependencies of the modes at 340 and 500 cm-1 exhibit softening with temperature increase,resulting from microstructure control,which may be due to small concentrations of Si,Zn,and Mn substitutions at the chain Cu(1)and plane Cu(2)sites.
基金Project suported by the National Science Fundation of China.
文摘The dependence of the effective penetration depthλe,on the external magnetic field in a high-Tc superconducter YBa2Cu3O7 has been measured by both dc and ac methods at liquid-nigtrogen temperature.It is found,thatλe increases rapidly with increasing external field and is 0.13~0.15mm in macroscopic scale.The Hcl of the specimen,about 800e at 77K here,can be determined more reliably by comparing dcλe with acλe.The difference betweenλedc andλeac,and the jumping ofλedc may indicate the characters of superconducting glass.
文摘We fabricated YBa2Cu3O7–d bulk ceramics with a domestic microwave oven and investigated the effect of pressure at the press procedure. If the pressure was not high enough, the ratio of BaCuO2 phase became large, estimated from x-ray diffraction (XRD) measurements. We found that the pressure should be 700 kgf/cm2 at least in order to suppress the BaCuO2 phase.
文摘YBa2Cu3Ox(YBCO) thin films grown on different substrates with and/or without Eu2CuO4(ECO) buffer layer were investigated by X-ray wide angle diffraction,reflection,diffuse scattering and topography.Theresults show that for the yttria stabilized ZrO2(YSZ) substrate,the presence of an ECO buffer layer improves the crystalline quality of the YBCO film,while a negative effect is observed for the SrTiO3(STO) substrate.The lateral correlation length for a sample grown on a YSZ substrate with ECO buffer Layer is much greater than grown on an STO subetrate.The STO substrate used has mosaic structure.2001 Elsevier Science B.V.All rights reserved.
