Chao Shen

Based on the previous work conducted by Fujii et al., NdBaInO₄ compounds present modest oxide-ion conductivities. Therefore, it has been an attractive system of significant interest. In this study, we attempted to partially substitute Ca for Nd and the total electrical conductivity was successfully improved due to the generation of oxygen vacancies. The synthesis, crystal structure, density, surface topography, and electrical properties of NdBaInO₄ and Ca-doped NdBaInO₄ have been studied, respectively. NdBaInO₄ and 10% and 20% molar fractions of Ca-doped NdBaInO₄ were synthesized through solid-state reactions. The crystal structure of them was obtained from Le Bail refinement of the XRD pattern, giving the result of the monoclinic structure, which belongs to P2₁/c space group. The highest total electrical conductivity of 4.91 × 10⁻³ S cm⁻¹ was obtained in the Nd_0.9Ca_0.1BaInO_3.95 sample at a temperature of 760 °C in the dry atmosphere and the activation energy was reduced from 0.68 eV to 0.58 eV when the temperature was above 464 °C (737 K) after doping the NdBaInO₄ with a 0.1 molar fraction of Ca²⁺. Moreover, the total conductivity of Nd_0.9Ca_0.1BaInO_3.95 in the wet atmosphere at moderate temperature was relatively higher than that in the dry atmosphere, which suggests that potential proton conduction may exist in wet atmospheres. In addition, the oxygen diffusion coefficients of Nd_0.9Ca_0.1BaInO_3.95 (D* = 1.82 × 10⁻⁸ cm²/s, 850 °C) was about two times higher than that of Nd_0.8Ca_0.2BaInO_3.90 (D* = 7.95 × 10⁻⁹ cm²/s, 850 °C) and was increased significantly by two orders of magnitude when compared with the oxygen diffusion coefficient of the undoped NdBaInO₄ (D* = 8.25 × 10⁻¹¹ cm²/s, 850 °C).

Based on the previous work done by Fujii et al., NdBaInO4 compounds present modest oxide-ion conductivities. Therefore, it has been an attractive system of significant interest. In this paper, the Ca element has been attempted to partially substitute for Nd and the total electrical conductivity has been successfully improved due to the generation of oxygen vacancies. The synthesis, crystal structure, density, surface topography and electrical properties of NdBaInO4 and Ca-doped NdBaInO4 have been studied respectively. NdBaInO4, 10% and 20% molar fraction of Ca doped NdBaInO4 were synthesized through solid state reaction and they were calcined at 1000 °C for 14 hours and sintered at 1440 °C,1430 °C and 1420 °C respectively. The crystal structure of them has been obtained from Le Bail refinement of the XRD pattern, giving the result of the monoclinic structure which belongs to P21/c space group. The size of particles processed with different ball milling time and surface topography have been detected by the scanning electron microscope. The total electrical conductivities of Nd1-xCaxBaInO4-x/2 (x = 0, 0.1 and 0.2) were measured in the dry atmosphere by AC impedance spectroscopy and Nd0.9Ca0.1BaInO3.95 exhibited the highest total electrical conductivity and the lowest activation energy. What is more, the total conductivity of Nd0.9Ca0.1BaInO3.95 in the wet atmosphere at moderate temperature is relatively higher than that in the dry atmosphere while this phenomenon was not found in NdBaInO4. Therefore, the excess conductivity suggests that potential proton conduction may exist in wet atmospheres. In addition, Ca-doped NdBaInO4 were chosen for the oxygen isotope exchange which aims to obtain the diffusion coefficient and surface exchange coefficient, and Nd0.9Ca0.1BaInO3.95 shows the highest diffusion coefficient and D* decreases with the increase of the molar fraction of the Ca element.