Study On Preparation And Properties For Nano-Style Perovskite-Type Oxides

Perovskite type compound oxides have stable structure and outstanding performance. The various oxide materials with multiplex component and complex structure may be prepared successfully according to the pattern of metallogeny. Thus,it has aroused an universal interest. In this article, the nano-style perovskite type oxides La_1-xSr_xMnO₃ with smaller grain sizes and better dispersion were prepared and the electric-catalytic activity of powders was researched adequately. La_0.8Sr_0.2MnO₃ massive sample was prepared under high pressure and agglomeration. The grain evolution regularity and various physical properties were researched for the samples which were prepared under high pressure. The optimum preparation condition and photo-catalysis were researched for La_1-xSr_xMnO₃ thin film on the slide glass base using sol-gel method and dip-coating technology.The heat decomposition of gel was analyzed by means of TG/DTA and FTIRS; The phase change were analyzed by XRD and its crystal grain size had been calculated; The size of particles and the dispersibility of powders are observed by TEM; The surface area of samples were tested by means of BET; All of above, the optimum preparation condition of perovskite nano-style oxides La_1-xSr_xMnO₃ by citric acid sol-gel method can be obtained.A kind of new technology is presented for preparing nano-style perovskite powder which has better dispersion. It was that absolute alcohol instead of water as the solvent. It was verified this method could remarkably improve the powders'decentralization and prevent original particles from reuniting. The electric catalysis of La_0.8Sr_0.2MnO₃ is superiors to the powders which were obtained by the common sol-gel method. It can improve the discharge voltage of air battery to 1.52 V. When the ampere density reaches 150 mA/cm2 and discharge voltage is 1.4 V, the battery can continuous discharge for 15 hours. Thus, the capability of zinc-air battery was increased greatly.Crystallization process of nano-style oxide powders by high-enemy ball milling with mixing La2O3,MnO₂ and CaO was investigated by using X-ray diffraction patterns and Sherre equation. Results indicated that the La_0.8Ca_0.2MnO₃ can be synthesized by ball milling18 h under room temperature. The particle size of the powders showed a firstly increasing and subsequent decrescent trend with extending milling time while the grain refinement is limited as time grows.The compact La_0.8Sr_0.2MnO₃ massive sample was prepared which crystal grain size less than 100 nm under high pressure and agglomeration. The relationship between relative density of biscuit and forming pressure was analyzed. The grain evolution was researched by XRD,Raman pattern,field emission scanning electron microscopy and the phenomenological kinetic grain growth equation. The results show that it was influenced by temperature and pressure. The grain growth rate under 3 Gpa is increased with increasing pressure while the rate is fall down as pressure continue rise when the agglomeration temperature below 300℃. The grain growth rate is all along increased with pressure increment when the agglomeration temperature over 300℃.The various physical properties of agglomeration samples under high pressure were studied by testing apparent density,micro-hardness and electromagnetism character. Experimental results indicate that the micro-hardness of samples after high pressure agglomeration was obvious increased and the apparent density is also increased along with pressure. The relative density is 99.48% when sample was prepared under 500℃and 5 GPa. When sintering temperature was 300℃, the resistivity of samples showed first increasing then decreasing trend with increasing pressure and the sample which were prepared under 5 GPa,300℃has obvious ferromagnetic character at room-temperature.The optimum preparation condition for La_1-xSr_xMnO₃ thin film on the slide glass base using sol-gel method and dip-coating technology was gotten by orthogonal test design method. The phase change was analyzed by XRD and its crystal grain size had been calculated. The result shows that the La_1-xSr_xMnO₃ thin film can be synthesized and average crystal grain size is 10.32 nm. We may see from the AFM Image that the film with four layers is more homogeneous; the surface roughness is less. The average thickness obtained from the step meter is 98.8 nm.La_1-xSr_xMnO₃ nano-style thin films have better photo-catalysis effect than LaMnO3. The photo-catalytic experiment shows that the de-coloration rates of Acid red A, Acid orangeâ…¡,Weak-acid yellow C-3GN, Direct green BE, Weak-acid blue C-RL have reached to 95.56%, 89.70%, 97.56%, 98.40% and 91.16% respectively in 9h.