Critical current density was measured at 4.2 K for MgB 2 strands with and without SiC additions. In some cases measurements were performed on longer (1 m) samples wound on barrels, and these were compared to magnetic measurements. Most measurements were performed on short samples at higher fields (up to 18 T). It was found that in-situ processed strands with 10% SiC additions HT at 700-800°C show improved H r and F p values as compared to control samples, with H r increasing by 1.5 T. At 900°C even larger improvements are seen, with H r reaching 18 T and F p values maximizing at 20 GN/m 3 .

Polycrystalline samples of (Gd1−xYbx)2O3 and (Gd1−xHox)2O3 (0.0 ≤x≤ 1.0) were synthesized by a sol–gel process. X‐ray diffraction data were collected and crystal structure and microstructure analyses were performed using the Rietveld refinement method. All samples were found to have the same crystal system and formed solid solutions over the whole range of x. For the system (Gd1−xHox)2O3, the cationic distribution over the two non‐equivalent sites 8b and 24d of the space group Ia were found to be random for all values of x. For (Gd1−xYbx)2O3, the distribution is random in the range 0.0 < x≤ 0.5 and preferential in the range 0.5 < x≤ 1.0. The lattice parameters are found to vary linearly with the composition x. Replacing Gd3+ and Yb3+, or Gd3+ and Ho3+, by each other introduces slight changes in relative atomic coordinates. Crystallite size and microstrain analyses were performed along different crystallographic directions and both are found to vary anisotropically with the composition parameter (x). The obtained values of microstrain are correlated with the distribution of the rare earth ions over the two cationic sites of the structure. The average crystallite size ranges from 45 to 144 nm and the root mean square (r.m.s.) strain from 0.018 to 0.409 × 10−2.

The mixed oxides Zn 1-x Mg x O (ZMO) were prepared as nano-polycrystalline powders and thin films by a simple sol-gel process and dip coating method. Thermogravimetric (TG) and differential thermal analysis (DTA) were used to study the thermal chemistry properties of dried gel. Structural and microstructural analysis was carried out applying x-ray diffraction (XRD) and Rietveld method. Analysis showed that for x < 0.25, Mg replaces Zn substitutionally yielding ZMO single phase, while for x ≥ 0.25 two phases are identified ZMO and MgO. Replacing Zn 2+ by Mg 2+ distorts the cation tetrahedrons and decreases the lattice constants ratio c/a of the wurtzite ZMO which deviate the lattice gradually from the hexagonal structure as Mg 2+ increases. These distortions are attributed to the difference in electronic configuration of the two cations which suppress the paraelectric-ferroelectric phase transition in the ZMO wurtzite.

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Mg x Zn 1-x O (x=0.01-0.3) nanoparticles were synthesized by the sol-gel technique using solutions of Mg and Zn based organometalic compounds. The electrical properties of Mg doped zinc oxide (ZnO) were studied within wide temperature range from 300 to 500 K under the N 2 gas flow (flow rate: 20 sccm) and in the frequency range from 40 Hz to 1 MHz for ac electrical measurements. The dc conductivities and the activation energies were found to be in the range of 10 -9 -10 -6 S/cm at the room temperature and 0.26-0.86 eV respectively depending on doping rate of these samples. The ac conductivity was well represented by the power law Aω s . The conduction mechanism for all doped ZnO could be related to correlated barrier hopping (CBH) model. The complex impedance plots (Nyquist plot) showed the data points lying on a single semicircle, implying the response originated from a single capacitive element corresponding to the nanoparticle grains. The crystal structures of the Mg x Zn 1-x O nanoparticles were characterized using X-ray diffraction. The calculated average particle sizes values of Zn 1-x Mg x O samples are found between 29.72 and 22.43 nm using the Sherrer equation.