Preparation Of Azo Powders And Research On Resistivity And Photoluminescence Properties

High quality AZO powders have a decisive influence on the performance of AZO films.AZO powders were prepared by one-step solvothermal method and coprecipitation method.When the AZO powders were prepared by one-step solvothermal method,the zinc source was zinc acetate dihydrate,the aluminum source was aluminum nitrate nonahydrate,the precipitating agent was sodium hydroxide,and the reaction solvent was ethylene glycol methyl ether.The effects of the amount of aluminum incorporated,reaction time,reaction temperature,alkali concentration and molecular weight of the dispersant on the resistivity of the prepared AZO powders were investigated.At the same time,the defects in the AZO powders were analyzed by fluorescence emission spectroscopy and the relationship between the defects in the powders and the conductivity of the powders were analyzed.When the AZO powders were prepared by the coprecipitation method,the zinc source was zinc nitrate hexahydrate,and the aluminum source is aluminum nitrate nonahydrate.The effects of aluminum doping amount,calcination temperature and different precipitants on the fluorescence emission spectra of the powders were investigated.The results shown that the incorporation of aluminum was 3%,the reaction time was 4 h,the concentration of precipitant NaOH was 0.6 mol/L,the reaction temperature was 250?,the dispersant PEG-1000 was added.The resistivity was minimum of 14.6 ?·m.The powder had the best crystallinity,the best dispersibility,and the narrowest particle size distribution.The minimum D50 was 3.76 ?m.Comparing the unit cell parameters of different AZO powders doped with aluminum,aluminum elements were incorporated into the crystal lattice of ZnO.With the incorporation of aluminum,the aspect ratio of the powders were reduced from 28.32 to 2.6.When the reaction time reached 4 h,the precursor was completely converted into zinc oxide.After the precursor was completely converted,the particle size distribution range of the powders became wider with time.The prepared AZO powders were subjected to a photoluminescence test at room temperature,and there were mainly seven peak positions.According to the formula,the defects in the powders corresponding to the peak positions were oxygen vacancies(about 380 nm),zinc interstitials(452 to 470 nm),zinc vacancies(484 to 494 nm),and oxygen-substituted zinc.(about 542 nm),the conductivity of the powders obtained by the emission spectrum was related to the content of oxygen vacancies in the powders.The AZO powders were prepared by coprecipitation method,and the precursor of AZO powders were subjected to differential thermal-thermogravimetric analysis.The dehydration process of the precursor was divided into three stages.After 400?,the AZO phase was basically formed.The exothermic peak at 450-500? was caused by grain growth and crystal phase formation.Compared with the one-step solvothermal method,the fluorescence emission spectrum of the co-precipitation method had no peak of oxygen vacancy at ?=380 nm,and its resistivity was higher than that of the AZO powders prepared by one-step solvothermal method,all at 350?·m.Comparing the cell parameters of the powders prepared by different methods,it is concluded that the coprecipitation method was not conducive to the doping of aluminum.As the calcination temperature increases,the aluminum element was more easily incorporated into the crystal lattice of ZnO.The use of different precipitants had no effect on the unit cell parameters of the crystal.The co-precipitation method obtained the peak position of AZO powder:450?470 nm was the peak position of zinc interstitial,480?500 nm was the peak position of zinc vacancy,and 500?550 nm was the peak position of oxygen-substituted zinc.The ultraviolet emission peak at ?=420 nm was aluminum doping.The calcination temperature had little effect on the defects in the powder.When the amount of aluminum was the same,the higher the crystallinity of the powder,the stronger the fluorescence emission peak of the powder,and the more the defect content in the powder.The reaction temperature was 600?,and the fluorescence emission peak of AZO-5 powder prepared by using the precipitant NH4OH was the strongest,and the defect content in the powder was the most.