Synthesis, Electrical Properties Of Zr_1-xM_xP₂O₇（M=In、Zn、Sc）

As well known, solid electrolyte materials are a kind of important functionalmaterials and have attracted much attention because of their potential application valuesand wide application prospects in solid oxide fuel cells （SOFCs）, gas sensors, steamelectrolyzes, separation and purification of hydrogen, hydrogenation anddehydrogenation of some organic compounds and ammonia synthesis at atmosphericpressure, etc.Compared to low-or high-temperature electrochemical devices, intermediatetemperature electrochemical devices have many advantages. Therefore, considerableeffort has been devoted toward the intermediate-temperature solid electrolyte materials.Recently, a new type intermediate temperature protonic conductor, AP2O7, is attractedconsiderable attention for their potential applications. Kwon et al. reported theconductivity of SnP₂O₇is above10^-2S cm^-1. It is difficult to dissolve in water and havehigher thermostability. Shaorong Wang et al. investigated the conductivity and theperformance of fuel cell of CeP₂O₇at intermediate temperate （50²50℃）. As amember of AP₂O₇, the ionic conduction and application have few report until now.In this article, a series of samples Zr_1-xM_xP₂O₇（M=In、Zn、Sc）were prepared bya solid state reaction and modified hydrothermal precipitation methods, andcharacterized with XRD、SEM. X-ray powder diffraction patterns show that the samplesare single cubic phase. Using the samples as solid electrolytes and porous platinum aselectrodes, the ionic conduction properties and electrical properties of these sampleswere investigated by means of impedance spectroscopy, isotope effect, gasconcentration cell at intermediate temperate in various atmospheres.We haven’t found any report about the performance of fuel cell of ZrP2O7and thedoped compound fuel cell so far. The performances of fuel cell based on Zr_1-xIn_xP₂O₇were investigated in this study. In addition, ZrP₂O₇-based ceramics have a few reported until now. The series of samples Zr_1-xM_xP₂O₇（M=Zn、Sc） ceramics were prepared by asolid state reaction and modified hydrothermal precipitation methods, and the ionicconduction properties were investigated by means of some electrochemical methods.Main works and results are as follows:1. The synthetic condition of ZrP₂O₇was investigated. The results indicated thatwhen Pini/Sn was3.0and the sample heat-treated at700℃for2h.2. Based on the optimum synthetic conditions mentioned above, the samplesZr_1-xIn_xP₂O₇（x=0.03,0.06,0.09,0.12） were prepared. The conducting properties of thesamples were investigated in the intermediate temperature range of100³00℃. It wasfound that the conductivities were affected by the doping level of In3+, and increased inthe order: σ （x=0.03）<σ （x=0.12）<σ （x=0.06）<σ （x=0.09）. It was also foundthat the samples were almost pure ionic conductors under wet hydrogen atmosphere at100²50℃. The H₂/air fuel cell using Zr0.91In0.09P2O7as electrolyte generated amaximum power density of16.9mW·cm^-2at175℃. The result indicated thatZr0.91In0.09P2O7may be a potential electrolyte candidate for intermediate temperaturefuel cell.3. A novel series of samples Zr_1-xZn_xP₂O₇（x=0.00,0.03,0.06,0.10）. The dopinglimit of Zn²⁺is6mol%. The dopant content x in the samples remarkably influenced theconduction properties. Conductivities increased in the order: σ （x=0.00）<σ （x=0.03）<σ （x=0.10）<σ （x=0.06）. The highest conductivity was observed to be1.85×10^-4S·cm-1for the sample of x=0.06under wet H₂atmosphere at600℃. The ionicconduction was contributed mainly to proton and partially to oxide ion in wet hydrogenatmosphere.4. The series of Zr_1-xSc_xP₂O₇ceramics was synthesized vis modified hydrothermalprecipitation method, XRD、 SEM were used to character the samples and itselectrochemical properties were studied by various electrochemical methods. In addition,we compared the sample of Zr_0.91Zn_0.06P₂O₇and Zr_0.91Sc_0.06P₂O₇ceramics.