Description

All studied samples (Bi3Nb1-yEryO7-δ (y=0.0-1.0), La1-xBixNb1-yWyO4 (x=0.0-0.5, y=0.0-0.2), La1-xAxMn1-yByO3+δ, где A= Sr, Bi, B= Ni, Cu (x=0.0-0.5, y=0.0-0.3)) were obtained using solid state method. Substituted lanthanum manganites were prepared by citrate-nitrate method additionally. A crystallographic structure of samples was refined using X-ray diffraction analysis and Rietveld full-profile method. An incommensurable modulated structure was observed for the LaNb0.90W0.10O4. The solid solution La1-xBixNb1-yWyO4 (x=0.1-0.5; y=0.1-0.2) with double substitution have not formed. Phase transitions from one crystal structure to another were found for some samples by high-temperature X-ray diffraction analysis and dilatometric measurements. The most thermal stable compounds are lanthanum manganites substituted by nickel and copper ions according to results of thermogravimetric analysis. Using laser diffraction an average particles size is about 10-20 μm for all samples prepared by solid state reaction and 1-5 μm in the case of citrate-nitrate method. A sintering density of ceramic samples determined by Archimed method is 90-95 % for electrolyte materials Bi3Nb1-yEryO7-δ и La1-xBixNb1-yWyO4 and 75 % for cathode ones La1-xAxMn1-yByO3+δ (A= Sr, Bi, B= Ni, Cu) (independing on synthesis method). These results were confirmed by scanning electron microscopy and it was shown the sintered briquettes have a homogeneous composition and grains with different shapes and sizes. Obtained values satisfy the requirements of a sintering density of ceramic materials used as electrolyte and electrode materials. The found values difference of thermal expansion coefficient of the electrode and electrolyte materials is permissible. According to results of the determination of a chemical compatibility the studying materials can be considered at joint application in electrochemical cells at temperatures lower than 600 °С. Among electrolyte materials the most electroconducting ones are substituted bismuth niobates, among cathodic ones – La1-xBixMnO3+δ with low bismuth ions content (with advantage for samples obtained by citrate-nitrate method). Unlike the composite with doped bismuth niobate in the case of lanthanum niobate using it can be observed a growth of electroconductivity values in comparison with values obtained for pure electrolytes. However in the case of using of composite electrodes (the mixture of lanthanum manganite and bismuth niobate in weight ratio 1:1) for electrochemical cells with Bi3Nb1-yEryO7-δ electrolyte in low temperature measurement region the obtained electroconductivity values are almost on one order higher than at the application of complex oxide electrodes (based on substituted lanthanum manganite).
StatusFinished
Effective start/end date05/02/201631/12/2017

Keywords

  • 31.15.19
  • RFFI
  • Kuibyshev Research Division