Preparation And Electrochemical Properties Of Zn-doped Alumina-based Proton Conductors

Since the twenty-first century,people have paid high and extensive attention to the research of ionic devices,making the development and application of ionic devices have a broad prospect.For example,In doped Ca Zr O₃ solid proton electrolyte made of perovskite type high-temperature proton conductor has been used in the smelting process of metal aluminum.However,its high-temperature stability is poor,and it is easy to decompose at high temperatures above 1273K.Therefore,it is of great significance to develop more stable proton conductor electrolytes.In this paper,Al_2-xZn_xO_3-α（x=0.004,0.008,0.012,0.016）series of solid oxide proton conductor electrolyte specimens were successfully prepared by the conventional solid-phase sintering method using Al₂O₃ and Zn O as raw materials.The physical structure,microscopic morphology and electrochemical properties of the electrolyte specimens were characterized and tested by X-ray Diffractometer（XRD）,Scanning Electron Microscope（SEM）and electrochemical workstation,respectively.The results of X-ray diffractometer tests showed that the Al_2-xZn_xO_3-α（x=0.004,0.008,0.012,0.016）series of solid oxide proton conductor electrolyte specimens prepared by the conventional solid phase sintering method had a pure alumina phase structure.According to the microscopic morphological analysis,it can be clearly observed under the SEM test at 3000X that the crystal grains of the specimens are relatively homogeneous and the densities of the ceramic specimens are high,with relative densities greater than 97%.The electrochemical properties of Zn-doped Al₂O₃ were clarified by measuring the electrical conductivity,isotope effect,electric potential test,and diffusion coefficient of the specimens under hydrogen-rich/oxygen-rich/water vapor-rich atmosphere by double-end AC method.Protons were found to be the main charge carriers in the temperature range of 1073 to 1473 K for Al_2-xZn_xO_3-αelectrolyte specimens in hydrogen atmosphere by isotope effect tests,and electric potential tests.The electrochemical impedance spectroscopy under hydrogen-rich/oxygen-rich/water-rich vapor atmosphere showed that the conductivity of the samples increased with the increase of temperature in the temperature range of 1073 K-1473 K.The conductivity of the samples with different Zn O doping amounts showed a pattern of increasing and then decreasing with the change of the doping amount x.The best electrochemical properties were obtained when the Zn O doping amount was x=0.012.The conductance activation energy(_（6）is in the range of1.01～1.62 e V in hydrogen-rich atmospheres.From the point of view of electromotive force measurement,the theoretical（computational）electrical potential matches the measured potential very well.In a hydrogen-rich atmosphere of 1073–1473 K,the proton mobility of Al_2-xZn_xO_3-αexceeds 0.90.In this work,we proved that Al_2-xZn_xO_3-αsample is a proton conductor.Their diffusion coefficients are all higher than 10^-7,and their diffusion coefficients reach 9.687×10^-6 cm²/s when the doping of Zn O is x=0.012,which turns out to be significantly lower than that of chalcogenide plasmonic conductors.In summary,Al_2-xZn_xO_3-αelectrolyte specimens can be successfully produced by the conventional solid-phase sintering method,and they are proton conductors in the temperature range of 1073 K～1473 K.Their excellent proton conductivity and stability lay the foundation for the development of industrial hydrogen determination sensors with wide testing temperature range,long continuous stable operation time,and accurate and efficient test results.