Preparation And Properties Study Of Lanthanum Chromate Based Light-absorbing Coatings

Lanthanum chromate(La Cr O₃)has high melting point and good thermal stability,and especially it is provided with excellent physical and optical properties after doping modification.Recently,it has received wide attention due to the potential applications in infrared radiation and absorption.In this paper,lanthanum chromate with perovskite structure of molecular general formula ABO₃,which is used as the basis to investigate the potential of its application in the field of photothermal conversion after A-site Ca²⁺doping and A/B-site Ca-Ni doping.Investigating the effect of doping concentration on the phase composition,microscopic morphology,surface valence and optical properties of lanthanum chromate powder,which is prepared by sol-gel method.Based on the homemade lanthanum chromate doped powder,the process of preparing light absorbing coating was studied,and the lanthanum chromate doped light absorbing coating was successfully prepared on the surface of alumina ceramic sheet by screen printing,focusing on the physical phase composition,surface and cross-sectional morphology and optical properties of the light absorbing coating.The main findings obtained are as follows:The most suitable sintering temperature was 1200?for the preparation of calcium lanthanum chromate powder with A-site Ca²⁺doping,and it was found that with the increase of Ca²⁺doping,the main peak would generally shift to the right with the increase of Ca²⁺doping ratio,and the crystallinity were all well behaved,and the powder microscopic morphology was nearly spherical particle composition,and its average particle size increased with the increase of Ca²⁺doping,but the particles were not uniform.At the same time the peak surface of Cr⁵⁺and Cr⁶⁺in the material increases with the entry of Ca²⁺in the crystal,and the concentration of oxygen vacancies increases,which increases the free carrier absorption.In the band range of 200-2500 nm,the doped powder samples have a wide absorption band,in which the highest absorbance of La_0.8Ca_0.2Cr O₃ can reach 91.3%,and with the increase of the calcium doping ratio,the impurity energy level is generated so that the forbidden band width Eg value decreases significantly from3.08 e V to 1.08 e V.The most suitable slurry composition ratio for the preparation of calcium lanthanum chromate coating by doping of A-site Ca²⁺is 1:1 for the organic carrier to powder mixture ratio.In the process of exploring the effect of the number of printed layers on the thickness and roughness of the coating.It was found that the best number of printed layers was two.The main diffraction peaks of the coated samples were shifted to a large angle with the increasing doping ratio of Ca²⁺,and the grain size of the crystals in the surface morphology of the coating also became larger with the increasing doping concentration of Ca²⁺,and when the doping concentration reached 0.2,the bonding between the grains began to appear and the coating formed a hole structure which was conducive to improving the spectral absorption of the coating.The absorption of the Ca²⁺-doped coating was significantly increased in the range of 200-2500 nm,and the absorbance of the La_0.8Ca_0.2Cr O₃-coated sample was able to reach 95.2%.Lanthanum chromate based powders and coatings were prepared by co-doping with Ca-Ni at A/B sites,and it was found that with the increasing proportion of Ni doping,the main diffraction peaks of the coated samples shifted to a small angle,i.e.,showed a tendency to shift to the left,and a hole structure was formed on the surface of the coatings,which was conducive to improving the spectral absorption of the coatings.When the Ni²⁺doping concentration is 0.2,the absorbance is raised to a maximum capable of reaching 97.8%,which fully demonstrates that Ca-Ni co-doped calcium lanthanum chromate has great application prospects in the field of optics.