Effect Of Nd, Sm, Gd, Dy And Sr Doping On Structure And Electrical Properties Of LaMnO₃

Solid oxide fuel cell(SOFC) is an all solid-state energy conversion device.SOFC is considered to be one of the most effective power system for its outstanding characteristics in 21st century.At present,SOFC runs commonly at about 1000℃.So it makes great sense to develop new pattern of electrode materials which have high ion and electrical conductivity at mesothermal temperature to raise its efficiency.In the present work,Nd,Sin,Gd,Dy and Sr doped LaMnO₃-based composite oxide powders are synthesized with citric acid sol-gel method.The powder is tested by FTIR, XRD to characterizeres the type of residual organic substances,crystal structure and crystal unit cell parameter.Bulk samples are obtained through press and then sintered at high temperature.Conductivity of bulk samples is analyzed through AC impedance measuring between 400 to 700℃and relations to composition or temperature are illuminated.The result shows that,the structure of the composite oxide synthesized by roasting the xerogel at 800℃for 4h is distorted based on LaMnO₃ structure because of the doping elements.Infrared spectrum shows that the wave number of absorption maximum of LaMnO₃,La_0.9RE_0.1MnO₃(RE=Nd,Gd,Dy)and REMnO₃ decrease with the decreasement of La and increasement of RE.The powder sample is compacted under the pressure of 13MPa and then sintered at 1100℃for 1h with the speed at 2℃per minute,and bulk samples with fine micromorphological features can be prepared.The RE-doping(RE=Nd, Gd,Dy) improves the conductivity of La_1-x-yRE_xSr_yMnO₃(y=0.10) notably;The Sr-doping decreases the conductivity of La_1-x-yNd_xSr_yMnO₃(x=0.10) but increases the conductivity of La_1-x-yRE_xSr_yMnO₃(x=0.1,RE=Gd,Dy);The conductivities of SmMnO₃ above 400℃are all higher than the ones of REMnO₃(RE=La,Nd,Gd,Dy).And the highest conductivity of SmMnO₃ is 0.0048 S·cm^-1 at 650℃.Compare with the conductivity of series of LSMO,the result shows that their quantity is similar.