Preparation And Electrochemical Properties Of CaZr_1-xSc_xO_3-?

In recent years,although the In-doped CaZrO₃ solid proton electrolyte has been applied to the industrial hydrogen sensor,CaZrO₃-based ceramics doped with In₂O₃ have high conductivity relative to other CaZrO_3-based systems,but at high temperatures,they easily decompose according to the reaction In₂O₃?s??In₂O?g?+O₂?g?,which results in a decrease in proton conductivity.To develop a CaZrO₃-based,high-temperature proton conductor with high conductivity and resistance to the reduced atmosphere,we used Sc as a substitute for In as the dopant in CaZrO₃.The electrochemical properties of the CaZr_1-xSc_xO_3-?were studied deeply,which laid a foundation for the development of industrial hydrogen determinator with wide temperature range,long continuous stable working time,accurate and efficient test results.In this paper,the proton conductor electrolytes of CaZr_1-xSc_xO_3-??x=0.06,0.12,0.18,0.24?were prepared by conventional solid-state sintering with CaCO₃,ZrO₂ and Sc₂O₃ as raw materials.The crystal phase structure of the CaZr_1-xSc_xO_3-??x=0.06,0.12,0.18,0.24?solid electrolyte specimens was characterized using X-ray diffraction?XRD,Made by Netherlands PAnalytical B.V.?.Scanning electron microscopy?SEM;FSEM,Germany Carl-Zeiss,Sigma 500?was used to examine the microstructures of the original samples.The diffraction patterns indicated a pure perovskite-type structure with all the major diffraction peaks matching those of crystalline CaZrO₃,which corresponds to PDF,and no peaks of impurity were observed.And the grain size is uniform and there was no obvious porosity.The average particle sizes were 1.04?m?x=0.0?,1.19?m?x=0.06?,1.47?m?x=0.12?,1.15?m?x=0.18?,1.08?m?x=0.24?,respectively.The relative densities were above 99%,which had reached the standard of relative density.It is shown that CaZr_1-xSc_xO_3-??x=0.06,0.12,0.18,0.24?has been successfully prepared.The conductivity of electrolyte samples were tested in hydrogen rich atmosphere,oxygen rich atmosphere and water vapor atmosphere,respectively.As x values ranged from 0.06 to 0.24,the total electrical conductivity first increased and then decreased,and it increased with an increase in temperature from the range of 573K¹473K.The performance was optimum when the doping amount of Sc was 0.12.The positive hole participates in electrical conduction besides H_i⁺at higher temperatures?1473 K or higher?in the oxygen-rich atmosphere;the oxygen vacancy participates in electrical conduction besides H_i⁺at higher temperatures?1373 K or higher?in the water-rich atmosphere.We measured the H/D isotope effect of the CaZr_1-xSc_xO_3-?specimens at temperatures from 573 K to 1373 K.The value of R_D⁺/R_H⁺were greater than 1.34,and the H/D isotope effect is significant at low temperatures?1273 K or lower?the proton is the dominant charge carrier in this temperature range.This experiment measured the emf of a hydrogen concentration cell of the CaZr_1-xSc_xO_3-?samples in the temperature range from 573 K to 1273 K.The theoretical?calculated?and measured emfs coincide and the migration rates of proton t_i were greater than 90%.This result also confirms that protons are the dominant carrier in the temperature range from573 K to 1273 K.The electromotive force test of CaZr_0.08Sc_0.12O_3-?proton conductor electrolyte sample at high temperature for 159h shows that the CaZr_0.08Sc_0.12O_3-?proton conductor electrolyte sample had good chemical stability.It can stable and effective work for a long time under high temperature.In this work,CaZr_1-xSc_xO_3-??x=0.06,0.12,0.18,0.24?perovskite oxide solid electrolyte materials were successfully obtained by a high-temperature sintering method,sintering at 1623 K and then at 1823 K for 10 h each.Based on the electrical conductivity measurements,the H/D isotope effect,and the emf of CaZr_1-xSc_xO_3-?,protons are the dominant charge carrier in the oxygen-rich atmosphere,hydrogen-rich atmosphere,and water-rich atmosphere at temperatures ranging from 573 K to 1273 K.At the same time,perovskite oxide solid electrolyte materials had excellent conductivity and chemical stability.It will lay a foundation for the development of metal liquid hydrogen sensors with wide temperature range,long continuous stable working time and accurate and efficient test results in the future.