We report here the structural, surface morphology, mechanical, and current voltage characteristics of Zn1-xMxO ceramic samples with various x and M （0.00≤〈 x ≤ 0.20, M = Ni, Cu）. It is found that the considered d...We report here the structural, surface morphology, mechanical, and current voltage characteristics of Zn1-xMxO ceramic samples with various x and M （0.00≤〈 x ≤ 0.20, M = Ni, Cu）. It is found that the considered dopants do not influence the well-known peaks related to the wurtzite structure of ZnO ceramics, while the shapes and the sizes of grains are clearly affected. The average crystalline diameters deduced from the SEM micrographs are between 2.06 μm and 4.8 μm for all samples. The oxygen element ratio is increased by both dopants. Interestingly, the potential barrier can be formed by adding Cu up to 0.20, while it is completely deformed by 0.025 Ni addition. The breakdown field can be enhanced up to 4138 V/cm by 0.025 Cu addition, followed by a decrease with further increase of Cu up to 0.20. On the other hand, a gradual decrease in Vickers microhardness is reported for both dopants, and the values in the Ni samples are higher compared to those in the Cu samples. The electricul conductivity is generally improved by Ni, while the addition of Cu improves it only in the over doped region （≥ 0.10）. These results are discussed in terms of the differences of valency and ferromagnetic ordering.展开更多
We report here the paraconductivity of ErBa2Cu3-xMxO7-δ （M = Zn and Fe） superconductors. The logarithmic plots of excess conductivity Δσ and reduced temperature C reveal two different exponents corresponding to c...We report here the paraconductivity of ErBa2Cu3-xMxO7-δ （M = Zn and Fe） superconductors. The logarithmic plots of excess conductivity Δσ and reduced temperature C reveal two different exponents corresponding to crossover temperature as a result of shifting the order parameter from 2 to 3. The first exponent in the normal field region is close to 1, in which the order parameter dimensionality （OPD） is 2. The second exponent in the critical field region is close to 0.5, in which the OPD is 3. The coherence length, interlayer coupling, interlayer separation and carrier concentration decrease with increasing doping content, and their values for Fe samples are different from those of Zn samples. While anisotropy is increased with increasing doping content, it is generally higher for a Zn sample than that for an Fe sample. We also estimate several physical parameters such as upper critical magnetic fields in the a–b plane and along the c axis （Bab and Bc）, and critical current density J at 0 K. Although Bab and Bc are generally increased with doping content increasing, the value of Bab is found to be twice more than that of Bc. A similar behavior is obtained for J （0 K） and its value is higher in the Fe sample than that in the Zn sample. These results are discussed in terms of oxygen deficiency, localization of carriers, and flux pinning, which are produced by doping.展开更多
文摘We report here the structural, surface morphology, mechanical, and current voltage characteristics of Zn1-xMxO ceramic samples with various x and M （0.00≤〈 x ≤ 0.20, M = Ni, Cu）. It is found that the considered dopants do not influence the well-known peaks related to the wurtzite structure of ZnO ceramics, while the shapes and the sizes of grains are clearly affected. The average crystalline diameters deduced from the SEM micrographs are between 2.06 μm and 4.8 μm for all samples. The oxygen element ratio is increased by both dopants. Interestingly, the potential barrier can be formed by adding Cu up to 0.20, while it is completely deformed by 0.025 Ni addition. The breakdown field can be enhanced up to 4138 V/cm by 0.025 Cu addition, followed by a decrease with further increase of Cu up to 0.20. On the other hand, a gradual decrease in Vickers microhardness is reported for both dopants, and the values in the Ni samples are higher compared to those in the Cu samples. The electricul conductivity is generally improved by Ni, while the addition of Cu improves it only in the over doped region （≥ 0.10）. These results are discussed in terms of the differences of valency and ferromagnetic ordering.
文摘We report here the paraconductivity of ErBa2Cu3-xMxO7-δ （M = Zn and Fe） superconductors. The logarithmic plots of excess conductivity Δσ and reduced temperature C reveal two different exponents corresponding to crossover temperature as a result of shifting the order parameter from 2 to 3. The first exponent in the normal field region is close to 1, in which the order parameter dimensionality （OPD） is 2. The second exponent in the critical field region is close to 0.5, in which the OPD is 3. The coherence length, interlayer coupling, interlayer separation and carrier concentration decrease with increasing doping content, and their values for Fe samples are different from those of Zn samples. While anisotropy is increased with increasing doping content, it is generally higher for a Zn sample than that for an Fe sample. We also estimate several physical parameters such as upper critical magnetic fields in the a–b plane and along the c axis （Bab and Bc）, and critical current density J at 0 K. Although Bab and Bc are generally increased with doping content increasing, the value of Bab is found to be twice more than that of Bc. A similar behavior is obtained for J （0 K） and its value is higher in the Fe sample than that in the Zn sample. These results are discussed in terms of oxygen deficiency, localization of carriers, and flux pinning, which are produced by doping.
