Investigation of the substitution process can provide a better understanding of the superconducting mechanisms in cuprous oxide materials. In this work the effects of substitution Lanthanum (La) for Gadolinium (Gd) on...Investigation of the substitution process can provide a better understanding of the superconducting mechanisms in cuprous oxide materials. In this work the effects of substitution Lanthanum (La) for Gadolinium (Gd) on the structure and oxygen content for x = 0.0 - 0.5 in the compound Gd1-xLaxBa2Cu3O7-δ (GLBCO-123 phase) have been investigated. Samples were synthesized by using a wet-mixing method from powders of Gd2O2, La2O2, BaO, CuO, and solution of HNO3. Based on the analysis of XRD data and SEM-EDXA, it confirms that the sample has formed the GLBCO-123 phase, as expected. It has been obtained that the lattice parameters a and c are increased while the parameter b is slightly decreased with increasing content of Lanthanum. The oxygen content slightly decreased and structure of the Gd1-xLaxBa2Cu3O7-δ phase changed from orthorhombic to tetragonal with increasing the content of Lanthanum.展开更多
Two kinds of Nd 1+ x Ba 2- x Cu 3O 7- δ , the sintered samples and zone melted samples, were treated in pure Ar at 950 ℃. The substitution of Nd ions for Ba ions in the Nd 1+ x Ba 2- ...Two kinds of Nd 1+ x Ba 2- x Cu 3O 7- δ , the sintered samples and zone melted samples, were treated in pure Ar at 950 ℃. The substitution of Nd ions for Ba ions in the Nd 1+ x Ba 2- x Cu 3O 7- δ before and after the heat treatment was investigated by XRD. In order to know the effects of heat treatment, the T c and J c of samples with and without the heat treatment in Ar were comparatively studied. The results show that the substitution of Nd for Ba decreases, whereas T c and J c increase after the treatment. The Nd 1+ x Ba 2- x Cu 3O 7- δ samples were oxygenated in pure oxygen at 300 ℃ . Based on the XRD spectra it was found that the samples with x <0.4 can transform from tetragonal phase into orthorhombic phase after the oxygenation, whereas in the sample with x >0.4 no phase transition occurs even after a long time oxygenation.展开更多
Polycrystalline YBa2Cu3O7-y （YBCO） and Y0.6Gd0.4Ba2-xNbxCu3O7-y （YGBNCO） compounds with 0≤x≤0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized b...Polycrystalline YBa2Cu3O7-y （YBCO） and Y0.6Gd0.4Ba2-xNbxCu3O7-y （YGBNCO） compounds with 0≤x≤0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized by X-ray difference （XRD） and scanning electron microscopy （SEM）. The transport properties were measured by the （FPP） method in the temperature range from 70 to 130 K. As the Nb content in the samples increased, a diffused phase indicating a niobium perovskite phase and a small amount of unidentified phase appeared. With the increase of Nb content, the superconducting transition temperature Tconset increased slowly with x≤0.125, and then it remained unchanged or slowly decreased with 0.125≤x≤0.225. It could be found that there was a slow decrease of zero-resistance temperature, Tcoffset, with the increase of Nb content. The larger transition width might result from the YBa2NbO6 phase, impurity and unidentified phases of the sample due to the Nb doping.展开更多
The Raman and infrared spectra, resistivity as well as thermoelectric power of Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ ( x =0, 0.1, 0.2, 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure character...The Raman and infrared spectra, resistivity as well as thermoelectric power of Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ ( x =0, 0.1, 0.2, 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr 2Cu 2.7 Mo 0.3 O 7- δ cuprates are different from those of RBa 2Cu 3O 7- δ . The variations of the microstructure in Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ with Nd doping affect the carrier distribution, so as a result the superconductivity changes. Furthermore, it is pointed out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic size effect in HTSC.展开更多
Since the discovery of high-T<sub>c</sub> superconductors, additions of proper elements to YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> system have been proved to be qu...Since the discovery of high-T<sub>c</sub> superconductors, additions of proper elements to YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> system have been proved to be quite effective in both mechanism researches and improvements of sample preparation technique. Recently, an interesting phenomenon in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> was reported by Feng Yong et al., i.e. when being doped with appropriate amounts of V<sub>2</sub>O<sub>5</sub>, samples which have been quenched in air from 900℃ to展开更多
文摘Investigation of the substitution process can provide a better understanding of the superconducting mechanisms in cuprous oxide materials. In this work the effects of substitution Lanthanum (La) for Gadolinium (Gd) on the structure and oxygen content for x = 0.0 - 0.5 in the compound Gd1-xLaxBa2Cu3O7-δ (GLBCO-123 phase) have been investigated. Samples were synthesized by using a wet-mixing method from powders of Gd2O2, La2O2, BaO, CuO, and solution of HNO3. Based on the analysis of XRD data and SEM-EDXA, it confirms that the sample has formed the GLBCO-123 phase, as expected. It has been obtained that the lattice parameters a and c are increased while the parameter b is slightly decreased with increasing content of Lanthanum. The oxygen content slightly decreased and structure of the Gd1-xLaxBa2Cu3O7-δ phase changed from orthorhombic to tetragonal with increasing the content of Lanthanum.
文摘Two kinds of Nd 1+ x Ba 2- x Cu 3O 7- δ , the sintered samples and zone melted samples, were treated in pure Ar at 950 ℃. The substitution of Nd ions for Ba ions in the Nd 1+ x Ba 2- x Cu 3O 7- δ before and after the heat treatment was investigated by XRD. In order to know the effects of heat treatment, the T c and J c of samples with and without the heat treatment in Ar were comparatively studied. The results show that the substitution of Nd for Ba decreases, whereas T c and J c increase after the treatment. The Nd 1+ x Ba 2- x Cu 3O 7- δ samples were oxygenated in pure oxygen at 300 ℃ . Based on the XRD spectra it was found that the samples with x <0.4 can transform from tetragonal phase into orthorhombic phase after the oxygenation, whereas in the sample with x >0.4 no phase transition occurs even after a long time oxygenation.
基金Project supported by the Council of the Scientific Research Projects at Konya University
文摘Polycrystalline YBa2Cu3O7-y （YBCO） and Y0.6Gd0.4Ba2-xNbxCu3O7-y （YGBNCO） compounds with 0≤x≤0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized by X-ray difference （XRD） and scanning electron microscopy （SEM）. The transport properties were measured by the （FPP） method in the temperature range from 70 to 130 K. As the Nb content in the samples increased, a diffused phase indicating a niobium perovskite phase and a small amount of unidentified phase appeared. With the increase of Nb content, the superconducting transition temperature Tconset increased slowly with x≤0.125, and then it remained unchanged or slowly decreased with 0.125≤x≤0.225. It could be found that there was a slow decrease of zero-resistance temperature, Tcoffset, with the increase of Nb content. The larger transition width might result from the YBa2NbO6 phase, impurity and unidentified phases of the sample due to the Nb doping.
文摘The Raman and infrared spectra, resistivity as well as thermoelectric power of Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ ( x =0, 0.1, 0.2, 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr 2Cu 2.7 Mo 0.3 O 7- δ cuprates are different from those of RBa 2Cu 3O 7- δ . The variations of the microstructure in Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ with Nd doping affect the carrier distribution, so as a result the superconductivity changes. Furthermore, it is pointed out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic size effect in HTSC.
文摘Since the discovery of high-T<sub>c</sub> superconductors, additions of proper elements to YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> system have been proved to be quite effective in both mechanism researches and improvements of sample preparation technique. Recently, an interesting phenomenon in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> was reported by Feng Yong et al., i.e. when being doped with appropriate amounts of V<sub>2</sub>O<sub>5</sub>, samples which have been quenched in air from 900℃ to
