Preperation And Properties Of Novel Rare Earth Sesquisulfides Red And Yellow Pigments

The rare earth sesquisulfides have received considerable interest because of their nice opatical and thermo-stability properties. As environment friendly materials, they can be used as substitutes for industry inorganic pigment comprising heavy metals ions (e.g. cadmium, chromium and lead ions) which are hazardous to the health and environment. The preparation routes were usually carried out under high temperature and the brightness and thermo-stability of the product need improvement still. Therefor, studies were focused on improving synthesis method and researching dopants, in order to leading low preparation temperature and improving product properties.Various methods were used for the synthesis of red-yellow pigments based onγ-Ln2S3(Ln=La, Ce), and the products were characterized via X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectrum, thermal analysis (TG-DSC) techniques, transmission electron microscope (TEM), scanning electron microscope (SEM) and elemental analysis. The detailed contents are as follows: 1. Cubic rare earth sesquisulfidesγ-Ln2S3 (Ln=La, Ce) were prepared from raw materials, which were comprised of alkali carbonate A2CO3 (A=Na, K) and rare earth oxide (La2O3, or CeO2) mixed via solid-liquide way with different ratio, by sulfurization under flowing CS2/N2 atmosphere at 800℃. It was found that high purity cubic rare earth sesquisulfides were obtained by doping enough content of alkali, and there was no carbon element in the products. Simultaneously, color property of the products was studied, and the differential-graphic method was used for searching the intrinsic-absorption ofγ-Ln2S3 for the first time.2. A new kind of red pigments-quinary sesquisulfideγ-Ce-Pr-Nd-Na-S was Prepared from the raw material, which was comprised of compounds of Pr-Nd oxides, CeO2 and anhydrous Na2CO3, by sulfurization under flowing H2S atmosphere at 1000℃. By comparison between products with and without Pr-Nd, It was found that milder sintering, more brightly colored, and more thermo-stable red pigments were obtained by introducing Pr-Nd properly.3. A kind of new red-yellow pigmentγ-Ce2S3/SiO2 was synthesized from the raw composite materials, which were based on sintered mesoporous silicon dioxide and coated with cerium nitrate and sodium chloride via impregnation method, by sulfurization under flow CS2/N2 atmosphere at 800℃. By comparison between products with and without carrier, It was found that, more brightly and colorful (from red to yellow) pigments were obtained by introducing sintered mesoporous silica.