Abstract
A Gd-doped ceria powder (GDC,Ce0.8Gd0.2O1.9) prepared from an oxalate precursor was hot-pressed at 1173-1673 K in an Ar atmosphere and annealed in air at 1273-1573 K to control the bulk density and grain size. Complex impedance of GDC with the microstructure of 0.27-3.8 μm average grain size and 93-98 % theoretical density were measured at 573-1073 K in air in the frequency range from 100 Hz to 2 MHz. It was possible to separate the sample resistance into bulk, grain boundary and surface layer resistance at 573-673 K. A linear relationship was observed between the capacitance (Cgb) of grain boundary and average grain size. The thickness of grain boundary was estimated to be 2-4 nm from the measured Cgb and Cb (capacitance of bulk) of GDC. The grain boundary conductivity at 573-673 K was influenced by grain size and showed a minimum value at around 3 A Gd-doped ceria powder (GDC,Ce0.8Gd0.2O1.9) prepared from an oxalate precursor was hot-pressed at 1173-1673 K in an Ar atmosphere and annealed in air at 1273-1573 K to control the bulk density and grain size. Complex impedance of GDC with the microstructure of 0.27-3.8 μm average grain size and 93-98 % theoretical density were measured at 573-1073 K in air in the frequency range from 100 Hz to 2 MHz. It was possible to separate the sample resistance into bulk, grain boundary and surface layer resistance at 573-673 K. A linear relationship was observed between the capacitance (Cgb) of grain boundary and average grain size. The thickness of grain boundary was estimated to be 2-4 nm from the measured Cgb and Cb (capacitance of bulk) of GDC. The grain boundary conductivity at 573-673 K was influenced by grain size and showed a minimum value at around 3 m. A good agreement was recognized between the theory and results for the grain boundary conductivity.m. A good agreement was recognized between the theory and results for the grain boundary conductivity.
