Preparation,characterization And Optical Properties Of Nanocrystalline Lanthanum Hexaboride Non-continuous Thin Films

Since LaB6 has excellent selective absorption in the near-infrared region,it has a promising application in automotive glass or building glass.At present,the most widely employed method is to prepare LaB6 nano-powder by mechanical grinding method and disperse it into the organic carrier to make laminated glass.Few studies were reported that LaB6 nanoparticles were deposited directly on glass by magnetron sputtering.There are two difficulties with LaB6 nanoparticles prepared by magnetron sputtering.One is to adjust the magnetron sputtering parameters and substrate' s surface treatment to deposite LaB6 particles on substrate meeting with the Volmer-Weber model.The other is to ensure that the depositional particles are crystallized,and the crystalline LaB6 with a certain size can show the selective absorption in the near-infrared region.Based on these two problems,the paper studies on the preparation,morphology,composition,roughness and other microstructures of the non-continuous films.The growth model,the transmittance of sunlight and heat insulation of the films were also investigated in this thesis.The surface roughness of the substrate was increased by the ion beam sputtering,and the growth model of the films on the substrate surface was changed.The optimal time of the ion beam processing was determined by the surface roughness of the substrate and the adhesion of LaB6 film and substrate.The particle size was controlled by adjusting the magnetron sputtering time.When the sputtering time was within 5 min,the size of LaB6 particles in the film was between 20 and 100nm with spherical or ellipsoid shape.Crystallinity of film was improved by the heat treatment process.Heating to 800? and heat preservation for 1h was determined by the thermal temperature of substrate material and heating resistance wire.LaB6 particles in the film had more uniform size and distribution,sharpened diffraction peak.The average crystallinity increased from 36.82%to 89.12%after heat treatment.The composition,morphology,roughness and growth of the film were studied by XRD,FESEM,AFM and XPS.Through the analysis of FESEM and EDS in different regions of the sample,the growth type of the films matched with the Volmer-Weber model.The ratio of La to B in the film was about 1:7,and LaB6 particles were randomly distributed on the basement surface.By AFM analysis of the film,the maximum growth rate was 30nm/min and the surface roughness was the highest when the sputtering time was 4min.By XRD analysis of the film,LaB6 preferential growth direction was[100].Heat insulation performance of LaB6 non-continuous film was calculated by numerical integration.It was concluded that LaB6 non-continuous films prepared by ion beam sputtering for 90s,magnetron sputtering for 4min,heating to 800? and heatpreservation for 1h agreed with the equations of Tvis/Tsol>1.8,K>1 and Tsol<0.15.That showed the non-continuous film had excellent selective absorption and heat insulation effects in near-infrared region.However,due to the low visible light transmittance of the solar spectrum,less than 0.45,the products still need to be improved to meet the requirements of automobile glass or building glass.