The Studies On Chemical And Physical Properties Of The Single Perovskite And Double Perovskite Composite Oxide

The perovskite-type composite oxide LaSrBMnO₆(B=Fe,Co) ,LaSrCoFeO₆;La_0.5Sr_0.5BO₃(B=Fe,Co,Mn); La-B-Ti-O(B=Mg,Ca,Sr,Co) and La-Co-V-O,La₂CoMnO₆,La₂MnVO₆ were synthesized by the sol-gel method and characterized by means of XRD,TPR,BET,FT-IR,TEM,the catalytic activity evaluation,conductivity and magnetic properties.We find that the single-phase perovskite-type oxides LaSrBMnO₆(B=Fe,Co), LaSrCoFeO₆ and La_0.5Sr_0.5BO₃(B=Fe,Co,Mn) were synthesized by the sol-gel using citric acid as complex agent. It is shown that LaSrFeMnO₆ showed a higher conductivity than LaSrCoMnO₆ and LaSrCoFeO₆ after 1100℃calcinations for 3h in 5H₂%/95%N₂. LaSrCoFeO₆ showed a better catalytic activity for methane combustion than LaSrBMnO₆(B=Fe,Co), which T₁₀(methane conversion of 10%) and T₉₀(methane conversion of 90 % ) were 460℃and 673℃respectively, and LaSrFeMnO₆ showed the best catalytic activity between 500-650℃.The chemical and physical properties of several of the single, double perovskite-type oxides were compared under the same condition. In the first group, LaSrCoFeO₆, La_0.5Sr_0.5CoO₃and La₍0.5_Sr_0.5FeO₃, LaSrCoFeO₆ had the best catalytic activity for methane combustion but the worst conductivity. In the second group, LaSrCoMnO₆, La_0.5Sr_0.5MnO₃ and La_0.5Sr_0.5CoO₃, La_0.5Sr_0.5MnO₃ had the best catalytic activity and conductivity. In the third group, LaSrFeMnO₆,La_0.5Sr_0.5MnO₃ and La_0.5Sr_0.5FeO₃, La_0.5Sr_0.5MnO₃ had the best catalytic activity and LaSrFeMnO₆ had the best conductivity.The La₂CoMnO₆, La₂MnVO₆ and La-Co-V-O were prepared by the sol-gel using citric acid as complex agent. The studies showed that single-phase perovskite-type oxides La₂CoMnO₆ and La₂MnVO₆ were synthesidzed after 1100℃calcinations for 3h in 5H₂%/95%N₂, but the system of La-Co-V-O was not synthesized single-phase. Meanwhile, we also compared catalytic activity for methane combustion and magnetic activity of LaSrCoMnO₆ and La₂CoMnO₆.Four systems of perovskite-type composite oxides La-B-Ti-O(B=Mg,Ca,Sr,Co) were prepared by sol-gel using glucose as complex agent. Experimental results show that La-B-Ti-O(B=Ca,Sr,Co) were not synthesized single-phase perovskite-type oxides and the La₂MgTiO₆ was synthesized after 500℃calcinations for 3h in the air. The catalytic activity of La₂MgTiO₆ was the best after 800℃calcinations for 3h in the air.