Narrow Results

To address the structural mechanisms associated with T_c variations induced by Co doping, two samples of the nominal composition (Ga_1-xCo_x)Sr₂(Tm_0.6Ca_0.4)Cu₂O_z with x = 0.5 and 0.7 have been prepared and studied by using neutron powder diffraction and transport measurements. In contrast to the x = 0.5 sample, which shows superconductivity around 35 K, the x = 0.7 sample does not exhibit superconductivity. The neutron powder diffraction studies indicate that both samples exhibit the 1212 structure with space group Ima2 and the Co atoms exclusively substitute for the Cu atoms located on the chain sites of the 123 parent structure. The depression in Tc of the x = 0.7 sample, compared to that of the x = 0.5 sample, is discussed in connection with oxygen content, disorder, and change in hole concentration on the superconducting planes.

A series of Bi${}_{0.8}$Ba${}_{0.2}$Fe${}_{1-x}$Co_xO₃ ($x=0.00$, 0.05, 0.10, and 0.15) samples were synthesized using the tartaric acid modified sol–gel method. The crystal structure of the prepared samples was analyzed by XRD, and the samples co-doped with Ba and Co were all rhombohedral distorted structures with the R3c space group. With an increase in the doping amount, a reduction in lattice parameters was observed along with crystallite sizes consistently being below 62nm. Mössbauer spectral analysis at room temperature reveals a good fit with two sextets and a doublet, all attributed to the Fe${}^{3+}$ state. This suggests that the charge balance within the samples is maintained through the generation of oxygen vacancies in the system. The hysteresis loops of all samples revealed the weak ferromagnetic of the Co-doped Bi${}_{0.8}$Ba${}_{0.2}$FeO₃ nanoparticles. With the increase in Co doping, the magnetic parameters such as saturation magnetization and coercive field significantly improved.

Co-doped ZnO/C composites derived from Co-doped MOF-5 were applied as the anode materials for Li-ion batteries (LIBs), which showed advanced capacity and rate performance. Their good electrochemical properties were attributed to the Co-doping and C complex which greatly enhance ZnO electrical conductivity, and the microporous and macroporous structure which augments the contact area between electrolyte and electrode shortening the diffusion path of Li ions as well as releasing the intense heat caused by Li alloying.

Thin films of Co-doped $\alpha$-MnO₂ have been deposited on Pyrex glass substrates by the sol–gel dip-coating method with Co concentrations of 1, 3, 5 and 7 at.%. The deposited thin films were characterized for their structural, morphological, optical and electrical properties. The XRD spectra confirm that all the samples have tetragonal phase of $\alpha$-MnO₂. FTIR spectra reveal the presence of Mn–O in all of the samples. AFM measurements indicate that the surfaces of films have been affected with cobalt content incorporation. Transmittance spectra of the undoped and Co-doped MnO₂ thin films were recorded by a UV–vis spectrometer. Optical gap was found to be in the 2.60–2.51-eV scale. This decrease is due to the presence of manganese vacancies and/or oxygen defects. From the complex impedance measurements that show semicircular arcs at different cobalt contents, an equivalent parallel $R_P{C}_P$ electrical circuit has been proposed.