Study On Microstructural Engineering And Physical & Chemical Properties For Ferrous Titanate

As functional materials,the titanates（calcium titanate,barium titanate,strontium titanate,etc.）in the perovskite structure have become the focus of research,the A position in the ABO ₃ structure is the fixed divalent ion.FeTiO₃is an n-type semiconductor material with the same[BO ₆]octahedron structure as ABO₃,but the variable valence Fe ion can cause valence state changes of A and B ions and cause crystal defects,such as oxygen vacancy.In addition,the microstructure of FeTiO₃ was controlled by changing the calcination atmosphere or doping the heterovalent ions,and the crystal defects can be further introduced.These changes would lead to the change of the physical chemistry properties.In this paper,the FeTiO₃ nano powder was prepared via sol-gel method,by reducing atmosphere calcine and valence ion doping to control microstructure,ion valence and defects.The preparation process parameters and ion doping effected on FeTiO₃ phase composition,ion valence,microstructure and defects are systematically studied.The adsorption,photocatalytic and physical and chemical properties of lithium ion battery cathode material were analyzed,and the mechanism of the phase composition,microstructure and crystal defect effect on the performance was discussed.The results show that the calcining atmosphere,calcining temperature,CO partial pressure and Fe/Ti ratio have great influence on the phase composition and ion valence state of FeTiO ₃.The main phase obtained by calcining in oxidizing atmosphere is Fe ₂TiO₅.Pure FeTiO₃ crystals can be obtained only under the reduction atmosphere and the calcination temperature ranges from 500℃to 700℃.Further increasing the calcination temperature FeTiO₃ will decompose decreased.CO partial pressure increase will cause FeTiO ₃ to decompose TiO₂and Fe₃C.Meanwhile,with the increase of CO pa rtial pressure,the content of concentration gradually increased.When the ratio of Fe/Ti is lower than 1:1,the phase composition of the sample is FeTiO ₃ and TiO₂,the sample is single-phase FeTiO₃with the ratio of Fe/Ti is 1:1,when the ratio is higher than 1:1,the phase composition were FeTiO₃,Fe₃C and Fe₃O₄.As the ratio of Fe/Ti increased,the concentration decreased.Nb-doping affects the phase composition,lattice constant,ion valence state,oxygen vacancy and energy band structure of FeTiO₃.When the Nb-doping amount is lower than 5mol%,Nb ions enter the FeTiO₃ lattice,and the sample is still single-phase FeTiO₃.When the Nb-doping amount is higher than 5mol%,TiO₂ phase will appear in the sample,and the proportion of TiO ₂ will increase with the increase of Nb-doping amount.The lattice constants a and c of FeTiO₃were gradually reduced by Nb doping,and the growth of FeTiO₃ grains was vacancy concentration increased.The valence band spectrum,the reflected electron energy loss spectrum and the first principle show that the band gap width of FeTiO₃ is narrowed by Nb doping.FeTiO₃ nanometer powder has excellent dye adsorption and photocatalytic properties.The adsorption process is based on the hydrogen bond action and the single-layer adsorption behavior under the electrostatic force.Nb doping and different Fe/Ti ratio samples have a photocatalytic degradation performance,and degradation of MB was better than CR.The catalytic mechanism as follows:for the Nb doping samples,Nb doping mainly affects the catalytic by reducing grains.For samples with different Fe/Ti ratios,is mainly through the formation of FeTiO₃-TiO₂ heterojunction to affect the photocatalytic efficiency.FeTiO₃shows good reproducibility in adsorption and photocatalysis.In addi tion,FeTiO₃ has magnetic,which can be separated and recycled by external magnetic field.As a lithium-ion battery anode material,the lithium storage performance of FeTiO₃ was studied.The results show that the morphology,phase composition and Nb doping have great influence on the lithium storage performance.The specific capacity of FeTiO₃ nanosheet sample is better than that of nano powder,the specific capacity of single-phase FeTiO₃ is better than that of FeTiO₃-TiO₂mixed phase,and the specific capacity of a certain amount of Nb doped FeTiO₃is better than that of undoped sample.The results show that the FeTiO₃ electrode has good multiplier and cycling performance.The 1Nb-FTO-S electrodes provide high specific capacity of 782.1 m Ah/g at 50 m A/g,which is superior to the currently study titanium base lithium ion battery cathode materials.