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Synthesis and Structure of New Hexagonal Perovskite Intergrowth, Influence of NiFe2O4 Dopant on the Photocatalytic Activity of TiO2

Author: YangJiaDong
Tutor: BieLiJian
School: Tianjin University of Technology
Course: Materials Physics and Chemistry
Keywords: The six-party perovskite Layered compounds Synthesis Structure Nickel ferrite Titanium dioxide Photocatalytic Structural phase transition Nanomaterials
CLC: TB32
Type: Master's thesis
Year: 2008
Downloads: 129
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Abstract


This dissertation includes two parts, the first part is a study of the synthesis and structure of the new hexagonal layered perovskite compounds, including papers first to the fourth chapter; second part of the content of nickel ferrite doped on TiO 2 structure and photocatalytic properties. Pyrolysis preparation using citric acid salt precursor, a solid-phase sintering process to explore the the hexagonal layered the perovskite compounds La 4 the Ba 2.6 of Ca 2.4 Mn 4 O 19 manganese replaced in the doping process discovered by Ba, Ca, Mn, O consisting of new material through repeated explorations The synthesis of a new compound for the synthesis conditions. The use of multi-crystal X-ray diffraction, electron diffraction methods to study the structure of the compounds; surface morphology of the samples and analyzed by SEM observation. Main results are as follows: 1. Through a series of experiments found that under the experimental conditions we selected the compound La 4 of Ba 2.6 Ca AND 2.4 Mn 4 O 19 Mn element may be a small amount of Cu, Co-substituted, with the increase in the relative content of Cu, Co, the compounds appear in the other phase, when the Cu, the relative content of Co reaches a certain value, the structure of the compound balance is destroyed, the formation of another phase; Fe, Ni substituted La 4 Ba 2.6 Ca < sub> 2.4 the Mn 4 O 19 in Mn incorporation small sample, the second phase is present, replace more compounds the original structure of the balance is broken, and the formation of a new phase of the unknown. Study new phase, we found that the novel compounds of Ba, Ca, Mn, O four elements together constitute a pure phase of the compound was synthesized by experiment, This compound Ba2.4Ca0.6MnO5. 125. The compound belongs to the hexagonal unit cell parameters a = 5.83460? C = 8.218982?, V = 242.3097? 3. The structure of the compound by powder X-ray diffraction data and the direct method, the structure deduced fitting using the X-ray diffraction data. The structure may be formed by 3H-type hexagonal perovskite structure unit and the [Ba2O2] layer arranged alternately. Hexagonal perovskite structure unit, Mn ions, and Ca ions occupy octahedral physical bit, octahedral coplanar or of vertices connected by Ca ions occupy 1/3 of the octahedral physical bit, the perovskite structure unit layer in the A-site ion Sites of occupied by Ba ions. In [Ba2O2 layer, 10% Ba atom is substituted by Ca. SEM image display of this compound is a layered structure, which is consistent with structure analysis result. Mn average oxidation state in the compound is 4.25. Doped nickel ferrite control to improve its photocatalytic properties of titanium dioxide phase transition as follows: coprecipitation and sol - gel prepared nickel ferrite and titanium dioxide nanopowders of Ni Ferrite doped changes in the crystal structure of titanium dioxide anatase → rutile \The results show that the efficiency of nickel ferrite doped inhibit titania phase transformation from anatase to rutile structure and significantly improve its photocatalytic activity, when the best doping concentration, the photocatalytic degradation of Eosin can be increased to about 2 times.

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