Research On The Preparation And Properties Of Molybdate, Tungstate And Titanate Thin Films By Soft Solution Processing Technique

Soft Solution Processing (abbreviated as SSP) is an environmental and ecological conscious technique for functional thin film fabrication, which was presented near the end of 20th century. Electrochemical syntheses method and hydrothermal syntheses processing are the important two methods of SSP. Comparing other methods for preparing functional thin films, these methods have some advantages over conventional thin films processings such as low energy consumption, high yield and one step formation of the thin films etc. So these methods may have great potential to application in this thesis.In this thesis, scheelite-type molybdate thin films (include BaMoO4, SrMoO4 and Ba1-xSrxMoO4) and tungstate thin films (include BaWO4, SrWO4, CaWO4 and Ba1-xSrxWO4) were prepared directly on molybdenum and tungsten substrates by constant current electrochemical method at room temperature respectively. By means of modern analyses techniques, such as XRD, SEM, EDAX, XPS and AFM, the influence of electrochemical conditions (include temperature, concentration of electrolyte, pH value of solution and current density etc.) on the formation of the thin films were investigated, and the optimum electrochemical processing conditions for preparing thetwo kinds thin films were obtained. The photolurninescenee properties of the as-grown molybdate and tungstate thin films at room temperature were investigated for the first time. BaTiO3 and Ba0.5SrofTiO3 thin films were prepared by hydrothermal synthesis method; the as-grown thin films were analyzed and characterized by using XRD, SEM, XPS and AFM; the impact of hydrothermal reacting temperature on the formation of thin films were studied in some detail.The main conclusions with innovative features acquired from the present work are as follows:(1) Soft Solution Processing technique for preparing functional thin films was put forward and applied to preparing advanced inorganic functional thin films; a series of molybdate and tungstate films with scheelite-type were prepared directly on metal substrates (molybdenum and tungsten foils) by using constant current electrochemical technique at room temperature; a series of titanate thin films with perovskite-type were synthesized directly on titanium flakes by hydrothermal method in our country for the first time.(2) The temperature has great affect on the morphologies of the as-grown thin films in constant current electrochemical technique. The as-grown thin films are compact and uniform at about room temperature or a little higher than room temperature (under 50 ); whereas when the deposition temperature is higher than 50 , it would lead to porous defect in the as-grown thin films, and the higher the temperature, the inferior the morphology of the as-grown thin films. The optimum electrochemical temperature is near room temperature.(3) The current density is the driving force for electrochemical reaction in the thin films formation process; the greater the current density, the quicker the electrochemical reaction, the more easily the nuclei formation, whereas the excessive current density would affect the quality of the as-grown thin films. So, the current density should be smaller, in view of the speed of electrochemical reaction, the optimum current density is about 1 mA/cm2.(4) Taking BaMoO4 thin film as an example, the processing conditions and the formation mechanisms of molybdate and tungstate thin films by electrochemical technique, and the optimum processing conditions of the two kinds of as-grown thin films above-mentioned were obtained.(5) By means of XPS and EDAX, the relationship between the composition concentration x of Ba1_xSrxMoO4 and Ba1.xSrxWO4 thin films and Sr/Ba in the starting electrolytes was researched in some detail, and the x is consistent with the percentage of Sr element in the starting electrolytes, so, the composition concentration x can be controlled by modulating the Sr/Ba in the starting electrolytes.(6) At room temperature, the photoluminescence properties of as-grown molybdate...