Bi 2 Sr 2 Ca 2 Cu 3 O x (Bi-2223) were prepared using a solid state reaction method at different sintering times and temperatures. Structural phase identifications have been done using X-Ray analysis and refinement by Reitveld method which proves the coexistence of Bi-2223 and Bi-2212 phases. The critical transition temperature T c and critical current density J c values were measured using superconducting quantum interference device magnetometer (SQUID) and by the magneto-optics technique. A remarkable rapid decrease to the diamagnetic signal in the magnetization versus temperature M(T) at 110 K and J c around 1.2 Â 10 7 A/m 2 at 5 K are confirmed for the Bi-2223 compound.

Pure barium titanate BaTiO3 (BT) and BT doped with two dierent transition elements Fe 3+ and Ni 2+ at 5 mol.% (BT5Fe and BT5Ni, respectively) as constant concentration in powder form have been prepared by sol gel method using barium acetate, titanium(IV) n-butoxide, iron and nickel nitrates as precursor materials. The microstructure of BT and the inuence of Fe and Ni dopants on it were investigated by X-ray diraction and Fourier transform infrared spectroscopy. X-ray diraction shows that tetragonal phase is dominant for pure BT sintered for 4 h at 800 • C. Scanning electron microscopy and transmission electron microscopy were used to study surface morphology and particle size distribution for BT5Fe and BT5Ni, respectively. The presence of hydroxyl defects were veried by Fourier transform infrared spectroscopy for (BaTi1−xFexO 3−x/2) (BTxFe), where x = 0.005, 0.01, 0.05, and 0.07 and (BaTi1−xNixO 3−x/2) (BTxNi), where x = 0.005, 0.01, 0.03, 0.05, and 0.07.

The complex dielectric permittivity (ε * = ε − jε ) and ac conductivity σ (ω, T) as a function of temperature (90-375 K) and frequency (0.4 kHz to ≈ 100 kHz) were measured in this work for polycrystalline samples of hydroxyl ammonium sulfate, (NH 3 OH) 2 SO 4 . The measured electrical parameters revealed the existence of a structural phase transition at T ≈ 312 K, which was further confirmed by a differential thermal analysis thermogram, where a clear endothermic peak centered at ≈ 312 K is observed. Regarding the charge transport mechanism, it is likely that the behavior of frequency-dependent conductivity follows the universal dynamic response σ (ω,T ) = A(T )ω s(T ) . Moreover, the temperature dependence of the frequency exponent s(0 s 1) suggests the quantum mechanical tunneling model to be the most likely one that describes the electrical transport mechanism. The data correlate with the crystal structure and the hydrogen-bonding system.

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