Abstract
Na0.5Bi0.44Ca0.06TiO2.97 ceramics were synthetized by conventional solid-state reaction. XRD measurement analysis shows that the Na0.5Bi0.44Ca0.06TiO2.97 sample is the single perovskite structures. The oxide ion conductivity of the Na0.5Bi0.44Ca0.06TiO2.97 sample was investigated by AC impedance spectroscopy measurement. The bulk conductivity of Na0.5Bi0.44Ca0.06TiO2.97 sample can arrive at 2.22×10-4 S/cm at 573 K in air atmosphere. By changing measuring temperature of dielectric frequency spectroscopy measurement, the activation energy E and pre-exponential factor τ0 are E= 0.81 eV, τ0=1.5×10-13 s for Na0.5Bi0.44Ca0.06TiO2.97 sample, respectively. Judging from the relaxation parameters, the dielectric loss peaks correspond to oxide ion via vacancies diffusion in Na0.5Bi0.44Ca0.06TiO2.97 sample. Compared with the same dopant amount Na0.5Bi0.5Ti0.94Mg0.06O2.94 compound, the better oxygen vacancy mobility and larger specific free volume Vsf might be responsible for the favourable oxide ion conductivity in the Na0.5Bi0.44Ca0.06TiO2.97 sample, indicating that calcium modified Na0.5Bi0.5TiO3 materials are promising for intermediate-temperature solid electrochemical devices.
Highlights
IntroductionOxide-ion conductors are extensively applied in many important technological devices such as SOFCs (solid oxide fuel cells), oxygen separation membranes and sensors
Oxide-ion conductors are extensively applied in many important technological devices such as SOFCs, oxygen separation membranes and sensors
It is worthy to note that increasing oxide ionic conductivity is the key factor of increasing the power density and lowering the SOFCs operational temperature
Summary
Oxide-ion conductors are extensively applied in many important technological devices such as SOFCs (solid oxide fuel cells), oxygen separation membranes and sensors. It is worthy to note that increasing oxide ionic conductivity is the key factor of increasing the power density and lowering the SOFCs operational temperature. In the past several decades, several different structure materials were investigated extensively such as fluorite, perovskite, intergrowth perovskite/Bi2O3 layers and pyrochlore.[1,2,3,4,5,6] At present, 8 mol% yttria-stabilized zirconia (8YSZ) has been extensively used in the high temperature devices for excellent oxide ion conductivity, negligible electronic conductivity, better thermal shock resistance and thermal stability in both reduction and oxidation atmosphere. The CeO2-based oxide ionic conductors show the higher ionic conductivity at the intermediate temperature. The problem that Ce4+ may be deoxidized into Ce3+ in reducing environment is needed to solve.[9]
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