| Eu3+doped Lu2O3is a kind of function materials that emit red light under theirradiation of X-ray or α,β, etc high-energy particles. Lu2O3was applied to more areas inresponse to the need for high-performance detectors for use in high-energy physics,nuclear medicine and geological prospecting. Ceramic scintillators have achieved moreand more people’s attention due to its stable performance, uniform multicomponentdopant, lower cost and simple preparation. The first step to prepare high-performanceceramics is to prepare the nanopowder with little agglomeration. The products werecharacterized by the scanning electron microscope (SEM), the X-ray powder diffraction(XRD) and photoluminescence (PL) measurements. The achieved results are as follows.1、Lu203:Eu3+phosphors were prepared by co-precipitation processLu2O3and Eu2O3with the molarity ratio19:1were dissolved in nitric acid. Thenitrate solution was added into the precipitant solution gradually and stirred continuouslyusing a magnetic agitator. The white and fluffy precursors were achieved after washed bydeionized water and dried in vacuum oven. They were sintered at different temperatures ina muffle furnace in air. SEM morphology of Lu203:Eu3+phosphors showed that thephosphor morphology obtained with NH4HCO3as the precipitant was beans-alikenanorods with uniform thickness. While the particles was agglomerative seriously withNH3H2O as the precipitant, they were ball shape about24nm. The phosphor withNH4HCO3-NH3H2O as the precipitant had uniform ball shape about20nm and exhibitedbetter microstructural morphology with weak agglomeration state. The best ratio ofNH4HCO3-NH3H2O is1:3. X-ray patterns of Lu2O3:Eu3+phosphors revealed thatcrystalline phase was formed with high sintering temperature. As the sintering temperatureincreased, the full-width at half-maximum (FWHM) of diffraction peak reduced, while theintensity increased. The results indicated that the average diameters ofNH4HCO3-NH3H2O precipitant were about20nm, which was corresponded with theresults of SEM. Luminescence spectra of Lu2O3:Eu3+phosphors displayed that the typicalemission of Eu3+with main bands at612nm. The luminescent properties of the phosphorwith mixed solution as the precipitants sintered at800℃were excellent.2、Hydrothermal method was used on the base of co-precipitation process to studythe influences of hydrothermal process on preparing powders.The samples prepared by ammonia water, ammonium bicarbonate and the mixedsolution of them as the precipitants was sealed in a teflon-lined stainless-steel autoclave of100ml capacity and heated at250℃for6h. For comparison, deionized water and glycol added as the reaction solvent respectively in the experiment. The product was achievedafter washed, dried and heat-treated at different temperatures. The results of SEM showedthat the powders achieved by different precipitants had different morphologies after thehydrothermal method, ammonium bicarbonate powder formed lamellar structure,ammonia powder formed rod structure. But they all showed good dispersion, it means thatthe hydrothermal method can reduce the powders’ agglomeration at some degree. Themorphologies of products achieved by different reaction solvent have obvious distinction,the powders achieved by solvent with big viscosity kept the same morphology as theprecursor, when the viscosity became small, its products’morphology also have somechanges. XRD results showed that the hydrothermal process promoted the process ofcrystallization, when the temperature rose to800℃, we can get nanopowders withexcellent features. The spectra measured for the sample with heat treatment heated at400℃exhibit obvious luminescence,while the powders made by co-precipitation processdid not have the emission of light. We can note that the the observed emission linesbecome sharp with the increase of temperatures, this relates to the increase of crystallinegrain and the decrease of flaws. The intensity of light maximized at800℃.3、Micro-emulsion method is a new technology of preparing Lu2O3nanopowders.Then ammonia water were added into the micro-emulsion system added by dilutenitrate solution gradually, the white and fluffy precursors were obtained aftercentrifugalization, washed by deionized water and alcohol and dried in vacuum oven.Lu2O3:Eu3+powder were achieved after sintered at800℃for2h in a muffle furnace in air.We also treated the products in hydrothermal method to study the change of the powder.The results of SEM revealed that the powders were ball shape about22nm, its dispersitywas better than the powders achieved by co-precipitation process with ammonia water asthe persistent. The morphologies of products also have obvious changes after the processof hydrothermal process, they became short rod from nanosphere, and its length increasedwith the rise of temperatures. The X-ray pattern of precursor powders showed that theproducts obtained after the process of hydrothermal method had LuO(OH) crystallinephase. The process of high temperature and high pressure make some powders’ phasechanged. PL showed that with increasing temperatures the emission peak became sharper,which was related to the increase of crystalline grain and the decrease of the defects.The results showed that powders achieved by NH4HCO3-NH3H2O mixed precipitantexhibited very effective luminescence and had spherical shape morphology and uniformparticle size distribution with better dispersion. Lu2O3crystalline phase was formed only ifthe temperature was high enough. The emission peak became sharper with increasingtemperature, but its internal structure may be destroyed when the temperature was too high, so800℃was appropriate temperature. Hydrothermal treatment promoted the growth ofpowders, and the solvent environments had obvious effect on the morphologies of theproducts. Micro-emulsion method is a effective way which can obtained uniformnanosphere with good dispersity at room temperature, the products’ luminescence werealso excellent than the other methods. |
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