Study On Synthesis Of Mg/Fe Spinel Ferrites Nanoparticles From Mg/Fe-LDH Microcrystallites Under Mild Conditions And Photovoltaic Study On N-Si(111) Electrodes Modified By MFe₂O₄(M=Mg, Co), TiCl₄ And MFe₂

Spinel ferrites, a kind of soft magnetic material with a structural formula of MFe₂O₄, has many properties such as low melting point, high specific heat, big expansion coefficient, low saturation magnetic moment and low magnetic transition temperature. It can be synthesized from LDH, layered double hydroxides, known as hydrotalcite-like material. Pure single crystal silicon, as an important semiconductor, has already been used in many areas, including molectron, communication technology, computer technology and automatic technology.In this paper, some results are realized, including conversion from Mg/Fe LDH to Mg/Fe spinel ferrites under mild conditions and synthesis single crystal silicon modified by different inorganic materials. All tasks as follows:1. The MFe₂O₄ is synthesized from M²⁺/Fe²⁺/Fe³⁺-LDH(M=Mg, Co) crystallites at different aged temperature under 1.0 atm Results indicate that the contents of spinel ferrites are increased with the samples' aged temperature going up. When the aged temperature is at 95℃, the saturation magnetization value of the transformed product is near to pure corresponding spinel ferrites which is reported by reference.2. A series of M(II)-Fe(II)-Fe(III)-LDHs with different ratio of M/Fe were synthesized and absorbed on surface of n-silicon (111) wafer flatly (concussed in ultrasonic bath). The spinel ferrites adsorbed on silicon wafer were obtained from the assemblies by calcinations. Results show that the spinel ferrites have a affection on photoelectric transmission to n-silicon (111) crystalline while the modified electrode is in HI/I₂ solutions as electrolyte. Photo-voltage (Upv) and photocurrent density (jpc) of the composite electrodes have changeable rules with different contents of spinel ferrites.3. The TiCl₄ was grafted on the surface of n-silicon (111) by the chemical bond of Si-O-Ti. The LDH obtained from step 1 was grafted on the modified silicon wafer. Research results display that the modifications from TiCl₄ have good photovoltaic effect in the solution of HI/I₂, with photo-voltage (Upv) and photocurrent density (jpc) -0.569 V and 0.39 mA·cm^-2, respectively. After graft MgFe₂O₄ on the modified silicon, the photo-voltage (Upv) is increasing to 0.581 V, but the photocurrent density of silicon wafer is decreasing to 6.38×10^-3 mA·cm^-2.