Preparation and Properties of (YCa)(TiMn)O3-d Ceramics Interconnect of Solid Oxide Fuel Cells.

(YCa)(TiMn)O3-d ceramics prepared using a reaction-sintering process were investigated. Without any calcination involved, the mixture of raw materials was pressed and sintered directly. Y2Ti2O7 instead of YTiO3 formed when a mixture of Y2O3 and TiO2 with Y/Ti ratio 1/1 were sintered in air. Y2Ti2O7, YTiO2.085 and some unknown phases were detected in Y0.6Ca0.4Ti0.6Mn0.4O3-d. Monophasic Y0.6Ca0.4Ti0.4Mn0.6O3-d ceramics were obtained after 1400-1500 °C sintering. Dense Y0.6Ca0.4Ti0.4Mn0.6O3-d with a density 4.69 g/cm³ was observed after 1500 °C/4 h sintering. Log σ for Y0.6Ca0.4Ti0.6Mn0.4O3-d increased from -3.73 Scm-1 at 350 °C to -2.14 Scm-1 at 700 °C. Log σ for Y0.6Ca0.4Ti0.4Mn0.6O3-d increased from -2.1 Scm-1 at 350 °C to -1.36 Scm-1 at 700 °C. Increasing Mn content decreased activation energy Ea and increased electrical conductivity. Reaction-sintering process is proved to be a simple and effective method to obtain (YCa)(TiMn)O3-d ceramics for interconnects in solid oxide fuel cells.

Effects of improved process for CuO-doped NKN lead-free ceramics on high-power piezoelectric transformers.

In this paper, the effects of the electrical proper- ties of CuO-doped (Na(0.5)K(0.5))NbO(3) (NKN) ceramics prepared separately using the B-site oxide precursor method (BO method) and conventional mixed-oxide method (MO method) on high-power piezoelectric transformers (PTs) were investigated. The performances of PTs made with these two substrates were compared. Experimental results showed that the output power and temperature stability of PTs could be enhanced because of the lower resonant impedance of the ceramics prepared using the BO method. In addition, the output power of PTs was more affected by the resonant impedance than by the mechanical quality factor (Q(m)) of the ceramics. The PTs fabricated with ceramics prepared using the BO method showed a high efficiency of more than 94% and a maximum output power of 8.98 W (power density: 18.3 W/cm(3)) with temperature increase of 3°C under the optimum load resistance (5 kΩ) and an input voltage of 150 V(pp). This output power of the lead-free disk-type PTs is the best reported so far.