Defect dipoles in acceptor-doped (K0.5Na0.5)NbO3-based ceramics have a significant influence on their electrical properties. The present study examined the influence of the sintering atmosphere on the electrical properties of MnO2-doped (K0.5Na0.5)NbO3. The poled and aged samples sintered in the Ar atmosphere depicted unusual behavior related to the formation of defect dipoles (Mn2+Nb‴−VO··)′, aligned in the poling direction having larger polarity. The S-E loop of the poled and aged MnO2-doped (K0.5Na0.5)NbO3 ceramics sintered in the Ar atmosphere revealed larger strains in the poling direction and restrained strains in the opposite direction. Furthermore, it is observed that the unipolar electro-strain could reach 0.28% (d33* = 800 pm/V) at 3.5 kV/mm, a value nearly 5.6-fold higher than those obtained in the air atmosphere (0.05%). This method based on the sintering atmosphere and process control provides a promising way to obtain substantial electro-strain values suitable for applications in high-displacement actuators.
The IDEAL-Cell concept is based on the junction between a PCFC anode/electrolyte section and a SOFC cathode/electrolyte section, through a mixed proton and oxide ion conducting porous ceramic membrane, operating in the temperature range 600-700°C. Recombination of ions takes place within the junction, or central membrane (CM), and water vapor is evacuated through open porosity. The first results on the fabrication of multilayered samples reproducing the IDEAL-Cell structure are reported here, together with electrochemical tests carried out on selected samples in order to evaluate the performances of the chosen materials and to demonstrate the feasibility of this innovative concept of fuel cell. Stable OCV and power generation were obtained in the multilayered structures. Anomalies in the I/V curves and impedance measurements under large perturbation could be considered as proofs of water formation inside the central membrane.
By conventional ceramics sintering technique, the lead-free 0.85Bi 0.5 Na 0.5(1 -x) Li 0.5x TiO 3 -0.11Bi 0.5 K 0.5 TiO 3 -0.04BaTiO 3 (x = 0-0.15) piezoelectric ceramics were obtained and the effects of Li dopant on the piezoelectric, dielectric, and ferroelectric properties were studied. With increasing Li addition, the temperature-dependent permittivity exhibited the normal ferroelectric-to-ergodic relaxor (FE-to-ER) transition temperature (T FE-ER , abbreviated as T F-R ) decreasing down to room temperature. The increasing Li content also enhanced the diffuseness of the FE-to-ER transition behavior. For composition with x = 0.15, a large unipolar strain of 0.37% (d à 33 = S max /E max = 570 pm/V) was achieved under 6.5 kV/mm applied electric field at room temperature. Both unipolar and bipolar strain curves related to the temperature closely, and when the temperature reached the T F-R , the normalized strain d
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