13Effect of Mg Doping on the Electrochemical Performance of CaHfO3 Solid Electrolyte AITranslate

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Chinese Library Classification Number:O646[理学—物理化学]

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Using CaCO₃,HfO₂ and MgO as raw materials,a series of CaHf_1-xMg_xO_3-δ(x=0.06,0.12,0.18,0.24,δis oxygen vacancy concentration,hereafter referred to as CHM)solid electrolytes were pre-pared by a high-temperature solid-state reaction method.The structure was characterized by XRD and SEM-EDS,the electrochemical performance under various conditions was systematically evaluated by elec-trochemical impedance spectroscopy,and the dominant temperature range of proton conduction was determined via the H/D isotope effect.The results show that all prepared CHM solid electrolyte samples exhibit a single perovskite phase with uniform and dense microstructure,and their relative densities exceed 98%,which is higher than that of the undoped sample.The conductivity of the CHM solid electrolytes first in-creases and then decreases with increasing Mg doping content,reaching an optimum at x=0.12,and in-creases significantly with increasing temperature.In the temperature range of 973~1373 K,the conductivi-ty of CHM solid electrolytes in H2-rich atmospheres(dry H2+wet H2)ranges from 6.94×10^-6S/cm to 2.83×10^-4 S/cm,with activation energies of 0.77~0.96 eV.In O₂-rich atmospheres(dry O₂+wet O₂),the conductivity ranges from 5.87×10^-6S/cm to 1.65×10^-3 S/cm,with activation energies of 1.34~1.49 eV.Meanwhile,a pronounced H/D isotope effect of CHM solid electrolytes is observed in the temper-ature range of 973~1173 K,indicating that proton conduction dominates.Above 1173 K,oxygen-vacancy and electronic conduction become predominant.The chemical diffusion coefficient of H+in the CHM(x=0.12)solid electrolyte ranges from 1.04×10^-6cm²/s to 7.95×10^-6cm²/s within 973~1273 K,with a diffusion activation energy of 70.822 kJ/mol.The above results indicate that Mg-doped CaHfO₃-based so-lid electrolytes exhibit good electrochemical performance and represent promising candidates for application in high-temperature molten metal hydrogen sensors.