The Synthesis, Characterization And Phase Transformation Of Gallium Oxide Hydroxide And Gallium Oxide Nanocrystals

In recent years, the group IIIA metal compound semiconductor materials ofgallium have been widely used in the field of electronics, optoelectronics andelectrochemistry. As an important semiconductor material, gallium oxide （Ga₂O₃） hasa band gap of Eg=4.9eV, its conductive properties and luminescence properties havearoused concern for a long time. Currently, gallium oxide has been widely used as gassensors, the electrode materials of the ultraviolet light electrical parts, the materialsand catalysts UV detection. Gallium nitride （GaN） is a newly developed new typesemiconductor material with a wide band gap. It is a direct band gap semiconductormaterial at room temperature, the band gap Eg=3.39eV. GaN has many characteristicsinclude high thermal conductivity, resistance to strong radiation and high-temperaturechemical stability, so it has been made important used in optoelectronic devices suchas high-power microwave amplifiers, ultraviolet light-emitting diodes （LEDs） of blueand violet and laser diodes （LDs）. The morphology and size of the gallium oxide andgallium nitride will affect its performance greatly, so in recent years, a large numberof studies aimed at the synthesis of gallium oxide and gallium nitride crystals whohave inerratic morphology and uniform size. However, most of the gallium oxide andgallium nitride synthesis methods exist many shortcomings of low yield, low-purity,the nanowires defects and other disadvantages, these disadvantages will limit thevariety of applications in nanodevices at some extent. Recently, after a lot ofexperimental studies, it was found that in many methods of preparations of thegallium oxide and gallium nitride crystals, gallium oxide or gallium nitride wasprepared by heat treatment of the precursor GaOOH is a simple and efficient way.This method can by the control to the morphology and size of GaOOH crystalindirectly to control gallium oxide and gallium nitride crystal morphology and size.Therefore, the control of synthesis and morphology of GaOOH nanomaterials, and the study of its characterization and performance has important significance.In this thesis, by using liquid-liquid interface reaction principle, respectivelycombined to hydrolysis and alcoholysis method to synthetize the differentmorphologies of GaOOH nanomaterials. And on this basis, the synthesis of GaOOHwere as precursors to synthetize gallium oxide nanomaterials. The main contents andresults are as follows:1. The benzene saturated solution of anhydrous gallium trichloride and deionizedwater were as reaction raw materials, CTAB was as surfactant, using liquid-liquidinterface reaction method, different concentration of CTAB of deionized water wasdropwise into the diluted of benzene saturated solution of gallium chloride, and thenafter the autoclave was sealed and heated to180°C for12hours, to give GaOOHsamples. By controlling the concentration of CTAB, and through used in liquid-liquidinterface in experimental process to control the morphology and size of the finallyobtained GaOOH samples. When the concentration of CTAB was5mmol/L, GaOOHhexagonal prism nanostructures were obtained, and size was about700⁹00nm. Noneed to adjust the pH value in the whole process, no vacuum environment, simpleoperation, high yield, morphology and size easy to control.2. The benzene saturated solution of anhydrous gallium trichloride and methanolwere as reaction raw materials, by the methanol dropwise into the diluted of benzenesaturated solution of gallium chloride and the autoclave sealed heating, finally gotGaOOH nanomaterials. By controlling the reaction temperature and time, and throughused in liquid-liquid interface in experimental process to control the morphology andsize of the finally obtained GaOOH samples. When the reaction temperature washeated to160°C, and reaction time was48hours, GaOOH nano-brush were obtained,and size was about700⁹00nm, the head of nano-brush can be small to10³0nm.Abandon the previous idea used water to offer hydroxyl, instead of using methanol asthe material to offer hydroxyl over the process of synthetizing GaOOH. This mothedhas greatly reduce the speed of the reaction, the morphology and size of the finalGaOOH was easy to control.3. The GaOOH samples synthetized by different methods were characterized by X-ray diffraction line （XRD）, scanning electron microscopy （SEM）, transmissionelectron microscopy （TEM）, the testing of infrared absorption spectroscopy （FTIR）from different angles.4. The GaOOH hexagonal prism nanostructures synthesized by the hydrolysismethod were calcined in air, under different conditions of temperature and time,synthetized the pure phase of α-Ga₂O₃and β-Ga₂O₃, and the coexistence phase ofα-Ga₂O₃and β-Ga₂O₃, the sample remained original morphology. At the same time,combined the DTA spectra of GaOOH and XRD patterns of the Ga₂O₃samplessynthetized by different calcination temperature, we discussed the possible paths inthe α-Ga₂O₃phase transition to the β-Ga₂O₃, and phase change mechanism.