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(1− x )PZT5/ x NiFe 2 O 4 ( x = 0, 0.2, 0.3, 0.4, 0.5 and 1, abb. PZT/NFO) ceramic particle composites were fabricated of commercial PZT5 powder and self-fabricated NiFe 2 O 4 by solid-state sintering at 1150 °C for 2 h. The formation of cubic spinel structure of ferrite phase and cubic perovskite structure of ferroelectric phase in the composites were confirmed by X-ray diffraction studies besides slight peaks of pyrochlore phase. The formation of pyrochlore phase could be restrained by increasing magnetic content and the ferroelectric behaviors of the composite were properly promoted at x = 0.2. On the other hand, remanant polarization ( P r ) of PZT/NFO composites monotonously increased according to the adding content of PZT5 except for x = 0.2. Vice verse, ferromagnetic properties would be dominant with increasing NiFe 2 O 4 phase. The direct magnetic field ( H dc ) and ac electric field ( E ac ) were applied to the composites simultaneously for magnetocapacitance behaviors measurement. As a result, the self-modulation of dielectric and impedance were found for PZT/NFO composites. More interestingly, the magnetocapacitance of the composite probably was not related to the magnetoresistance as reported a lot but to the piezomagnetoeffects as expected. The PZT/NFO ceramic particle composites should be prospectively applied in multistate memories and else fields.

Ca 1−3 x /2 Bi x Cu 3 Ti 4 O 12 ( x = 0.0–0.3) ceramics were prepared by the conventional solid-state reaction method. X-ray powder diffraction analysis confirmed the formation of cubic CCTO phase except for subtle peaks of CuO. SEM micrographs suggested that the morphologies of doped CCTO ceramics had been sheet-like for high Bi-doping amount, and the dominant grain size decreasing could be seen for the small content of Bi-doping CCTO. Dielectric properties of pure and doped CCTO were investigated in a broad temperature range of 20–420 K. The results showed that bismuth doping could decrease the dielectric loss but suppress the dielectric temperature stability at the same time. Bi doped CCTO ceramics presented different relaxation properties. As to pure CCTO and BCCTO ( x = 0.3) only one MW relaxation (Relaxation I) could be found, which moves to higher frequency with temperature increasing. However, two relaxation processes (Relaxation I and II) appear for BCCTO ( x = 0.1–0.2). By means of complex impedance spectra analysis and Arrhenius fitting, we successfully separated the different conductive segments and explained the mechanisms of the two relaxation processes. Relaxation I appeared at low temperature could be attributed to the V O doping energies inside CCTO grains which did not showed significant changing of activation energy after bismuth doping. For Relaxation II at higher temperature than Relaxation I, with activation energy obviously depending on the Bi-ion concentration, may be related with the V O point defects at the grain boundaries.

Pure and Pr6O11-doped CaCu3Ti4O12 (CCTO) ceramics were prepared by conventional solid-state reaction method. The compositions and structures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of Pr-ion concentration on dielectric properties of CCTO were measured in the ranges of 60 Hz–3 MHz and 290–490 K. The third phase of Ca2CuO3 was observed from the XRD of CCTO ceramics. From SEM, the grain size was decreased obviously with high valence Pr-ion (mixing valence of Pr3+ and Pr4+) substituting Ca2+. The room temperature dielectric constant of Pr-doped CCTO ceramics, sintered at 1323 K, was an order of magnitude lower than the pure CCTO ceramics due to the grain size decreasing and Schottky potential increasing. The dielectric spectra of Pr-doped CCTO were flatter than that of pure CCTO. The loss tangent of Pr-doped CCTO ceramics was less than 0.20 in 2 × 102–105 Hz region below 440 K. The complex impedance spectra of pure and Pr-doped CCTOs were fitted by ZView. From low to high frequency, three semicircles were observed corresponding to three different conducting regions: electrode interface, grain boundary and grain. By fitting the resistors R and capacitors C, the activation energies of grain boundary and electrode contact were calculated. All doped CCTOs showed higher activation energies of grain boundary and electrode than those of pure CCTO ceramics, which were concordant with the decreasing of dielectric constant after Pr6O11 doping.

The structure and martensitic transition (MT) temperatures of Ni 44 Mn 45 Sn 10 R (R = Al, Ga, In and Sn) alloys were investigated. Valence electron concentration and cell volume are two main factors affecting the MT temperatures in Ni–Mn based Heusler alloys. Our results indicated that the MT temperatures do not vary monotonously with either of the two factors, but increase with the increasing of electron density. Combining the two factors, electron density might be a more appropriate parameter to describe the variations of MT temperatures.