Synthesis And Electrical Conductivity Of ABO₃ Perovskite Type Of Ceramics

High-temperature proton conductors of ABO₃ perovskite have potential applications in fuel cells,gas sensors,membrane separators and membrane reactors,etc.Since proton conduction in SrCeO₃ perovskite was discovered by Iwahara,many another high temperature proton conductors have been found one after another.The BaCe(1-x)Er_xO_3-αceramics were synthesized successfully via microemulsion methods in this study.And some kinds of electrochemical methods were used to study the proton conduction behavior at 300～800℃by using the BaCe_1-xEr_xO_3-αceramics as solid electrolyte.We attained some important results as follows:(1)BaCe(1-x)Er_xO_3-αceramics were synthesized successfully via microemulsion method.The high sinter temperature(1500℃)has been lowered successfully.(2)The proton conduction in BaCe(1-x)Er_xO_3-α,ceramics on intermediate temperature(300℃-800℃)was studied.It is a pure proton conductor on this temperature and proton conductivityσH⁺ =2.54×10^-2S·cm^-1 at 800℃higher than using solid state method at 1000℃.(3)Ammonia was synthesized at atmosphere pressure successfully by using BaCe_0.95Er(0.15)O_3-αceramic as a solid electrolyte, and the efficiency of electrochemical prton was about 40%;and the rate of ammonia formation is 9.15×10^-10mol·s^-1·cm^-2.Ishihara reported in 1994 that LaGaO₃ doped with Sr and Mg is a pure oxide-ionic conductor over a wide range of oxygen partial pressures(1～10²⁰atm),and it is considered as a promising candidate electrolyte for intermediate temperature fuel cell.The composite electrolyte of La_0.9Sr_0.1Ga_0.9Mg_0.1O_3-α—NaCl(1wt%)was synthesized by a solid-state reaction method.The structure and properties were determined and characterized through XRD,AC impedance spectroscopy,hydrogen concentration cell and hydrogen electrochemical permeation(pumping)methods. X-ray powder diffraction pattern shows that the ceramic sample was of a single perovskite-type LaGaO₃ and the impurity phases could be restrained effectively after doping certain amount of NaCl.The observed rate of electrochemical hydrogen permeation was close to the theoretical rate,verifying that the ceramic sample was almost a pure proton conductor and the proton conductivity was 0.082S·cm^-1at 1000℃under a hydrogen atmosphere.The Nd_0.95Ca(0.05)AlO_3-α,La_0.9Sr_0.1In_1-xZn_xO_3-α,ceramics were synthesized via sol-gel method in this study,and its electrochemical properties were studied by some kinds of electrochemical methods.It has discovered that Nd_0.95Ca_0.05AlO_3-αceramic can transfer proton in some extent.It is found that BaCe_1-xEr_xO_3-αand La_0.9Sr_0.1Gao_0.9Mg_0.1O_3-α—NaCl(1wt%)ceramics are good proton conductors,having potential applications.Nd_0.95Ca_0.05AlO_3-αceramic can transfer proton in some extent,It is a mixed conductor of proton and electron under a hydrogen atmosphere.La_0.9Sr_0.1In_1-xZn_xO_3-αceramics are worst proton conductors in these four ones.It is reduced easily under a hydrogen atmosphere,having poor applications.