Preparation And Properties Of Rare Earth Sulfide Pigments

The preparation of traditional inorganic pigment is simple and cheap,but some inorganic pigments contain noble metal ions,which is hazard to environment.Organic pigments are brightly colored and strong coloring powered,however,it is expensive for the preparation.Rare earth sulfide pigments are gradually focused because of their bright color,good chemical stability,absorption of ultraviolet rays,non-toxicity and environmental benign.Thus,in recent years,to the facile and cheap preparation of rare earth sulfide pigments with low cost has become a research hotspot.In this paper,red cerium sulfide pigments,red lanthanum-cerium sulfidepigments,yellow lanthanum sulfide pigments,and yellow green praseodymium sulfide pigments were successfully synthesized via two facile solid-solid and gas-solid methods with great potentials for large-scale production.The rare earth sulfide pigments obtained by solid-solid method and gas-solid method have the bright color,small particle size and good thermal stability.The preparation methods are relatively environmental benign.The main research contents were s(1)A solid-solid method was deveolped for synthesis of rare earth cerium sulfide pigments by calcining a mixure raw material containingcerium compund,sulfur powders withcarbon powders,and sodium carbonate at a certain amount of proportionunder high temperature.Meanwhile,a gas-solid method was also explored for synthesis of same rare earth cerium sulfide pigments by calcining a mixture of raw materials containing cerium precursors andsodium carbonates in CS₂datmosphere under high temperature.The composition,structure,particle size distribution of the of cerium sulfide red pigment were studied by menas of XRD,SEM,UV-vis absorption spectra and TG analysis.The color properties of the pigments were analyzed according to the international standard lighting system of CIE-1931 and CIE-1976.(2)Based on the above preparation,lanthanum was introduced to cerium sulfides to modulate the color properties.Thus,lanthanum-cerium sulfide composite pigments were prepared by solid-solid method and gas-solid method.The composition,structure,particle size distribution of the of lanthanum-cerium sulfide red pigments were studied by menas of XRD,SEM,UV-vis absorption spectra and TG analysis.The color of lanthanum-cerium sulfide red pigments was adjusted by changing the molar ratio of lanthanum/cerium,calcination temperature,and alkali metal doping amount.By analyzing the color properties of lanthanum-cerium sulfide red pigments according to the international standard lighting system of CIE-1931 and CIE-1976,it is found that the thermal stability and color properties of the lanthanum-cerium sulfide red pigments are obviously improved.The color of the lanthanum-cerium sulfide red pigments can reach the chromaticity coordinate of L*=41.2,a*=36.2,and b*,which shows great advantages over the ordinary chromaticity cerium sulfide red pigments in all aspects.(3)The synthesis of other rare earth-based sulfides pigments was explored to expand the color requirements for various industrial applicaitons.The lanthanum sulfide yellow pigments and praseodymium sulfide green pigments were prepared by solid-solid method and gas-solid method.The preparation conditions of component ratio,calcination temperature and doping amount were optimized.The composition,structure,particle size distribution of the of the lanthanum sulfide yellow pigments and praseodymium sulfide green pigments were studied by menas of XRD,SEM,UV-vis absorption spectra and TG analysis.The color properties of the lanthanum sulfide yellow pigments and praseodymium sulfide green pigments further were analyzed according to the international standard lighting system of CIE-1931 and CIE-1976.Our research may provide effective preparative methods f for developing different coloring pigments for various practical applicaitons.