Fabrication Of CoAl₂O₄ Ceramic Pigments And Effects Of Rare Earth Doped On Luminescence Properties

The chroma of CoAl₂O₄ ceramic pigments that fabricated by many preparation methods is low,results in limited application in ceramic glaze,enamel glaze,ceramic products,3D printing and other aspects.In some special fields,such as the permanent color and the anti-counterfeiting weathering coating,the anti-counterfeiting function of ceramic pigments were needed.In this project,effects of preparation processes on microstructure and color performances were investgated,and fluorescence properties were obtained by doped rare earth in order to obtain CoAl₂O₄ ceramic pigment with high chroma and anti-counterfeiting function.It has important scientific significance and application value for the development of new applications of ceramic pigments.The results are as follows:CoAl₂O₄ ceramic pigments were prepared by co precipitation method.It was found that the Co/Al ratio,the pH value of the solution,the calcination temperature and the content of dispersant could affect the color performances of CoAl₂O₄ ceramic pigments.The highest purity and chroma of CoAl₂O₄ ceramic pigment was got when the Co/Al ratio is 0.7:2,the pH value is 11,the calcination temperature is 1200 oC,dispersant cotents are 2% PVP and 0.4% CTAB.Essential factors affecting the color of CoAl₂O₄ ceramic pigment are the Co content,the valence state of Co ion and the coordination number.It may produce Co³⁺ or entered into the eight surface space of the spinel structure,and the coordination field of Co ions was changed when the content of Co is too high,thus different colors were obtained.The brightness and chroma of CoAl₂O₄ coating were improved after high temperature sintered at 1300 oC.CoAl₂O₄ coating with high Co/Al ratio was still presented blue due to the partially inverse spinel structure was formed,and the coating also has good chemical stability.CoAl₂O₄ ceramics have fluorescence properties by rare earth doped.It was found that phase compositions and color properties of CoAl₂O₄ ceramic pigments were unchanged basically when the Er³⁺ was doped,but the upconversion effect was found in the 950 nm infrared band.Doping Er³⁺ can enhance the upconversion luminescence intensity of CoAl₂O₄,and the optimum doping content is 1mol%.Co-doping Er³⁺/Yb³⁺ formed the oxides when the Yb³⁺ doping content is more than 6 mol%,which affects phase compositions and color performances of CoAl₂O₄ ceramic pigments.The doping of Yb³⁺ can reduce the green luminescence intensity of upconversion luminescence effect,but the red luminescence intensity increases.Rare earth doped CoAl₂O₄ ceramic pigments can be incorporated into special inks,paints,coatings,or used as anti-counterfeiting mark by the 3D printing,using characteristics that are the up conversion luminescence properties under the infrared laser.