Synthesis And Properties Of ZrSiO₄/Cd(S_1-xSe_x) Inclusion Pigments

Cadmium sulphoselenide(Cd(S_1-xSe_x)) is a colorant with colorful hues. In case of Cd(S_1-xSe_x), increasing S content gives red to yellow. However, Cd(S_1-xSe_x) is unstable and will be oxided when temperature above 700℃. Zircon(ZrSiO₄) is used as inert matrix due to its thermal and chemical stability towards glassy phases. Therefore, more and more attention has been paid to ZrSiO₄/Cd(S_1-xSe_x) inclusion pigment. Recently, the common way for preparing this pigment is solid phase sintering technique. The defect is inclusion ratio is low(generally<10%) and most of Cd(S_1-xSe_x) is oxidized to colorless material at high temperature. For this reason, developing new method for high inclusion ratio ZrSiO₄/Cd(S_1-xSe_x) pigment has important theoretic significance and economic value.In this paper, Cd(S_1-xSe_x) colorant was prepared by precipitate hydrothermal method firstly. Then, ZrSiO₄/Cd(S_1-xSe_x) pigment with high inclusion ratio was prepared via hydrothermal and microemulsion method, respectively. Structure, morphology and hues were characterized by X-ray diffractomentry(XRD), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDAX) and CIE chromaticity. The obtained pigment was used into glaze in order to analysis the coloring properties at high temperature. Furthermore, inclusion mechanisms were analyzed as well.Cd(S_1-xSe_x) colorant was prepared by precipitate hydrothermal method as Cd(NO₃)₂·4H₂O, Se powder and Na₂S·9H₂O for raw materials. NH₃·H₂O used to pH regulator. The results indicate that, with precipitate reaction, Cd(S_1-xSe_x) continuous substitute solid solution with low crystallinity is synthesized. The mechanism is Se^2- substitutes S^2- of CdS. But after hydrothermal reaction, the Cd(S_1-xSe_x) with higher crystallinity is obtained and structure is better. In addition, yellow hues decrease and red hues increase. The molar ratio of S/Se has a crucial effect on the colorant's hues; pH value and hydrothermal reaction conditions also have a very important influence. ZrSiO₄/Cd(S_1-xSe_x) inclusion pigment was prepared by hydrothermal method as ZrOCl₂, Na₂SiO₃, Cd(NO₃)₂·4H₂O, Se powder and Na₂S·9H₂O for raw materials. NH₃·H₂O, NaOH and CH₃COOH used to pH regulator. NaF used to mineralizer. Results show that, when pH value controls about 4, the addition of mineralizer is 4%, C_Na2S is 0.6M, hydrothermal condition is 180℃for 10h, ZrSiO₄/Cd(S_1-xSe_x) ratio is 2 and Zr/Si ratio is 1.0/1.0, pigments with acid treatment have higher hues and inclusion ratio(47.69%). XRD patterns show that sample with well crystallinity and without secondary crystalline phase, it indicates ZrO₂ reacts with SiO₂ and forms ZrSiO₄ completely. Transmission electron micrpscopy(TEM) analysis shows that, the average size of sample is 20-30nm and the inclusion thickness is 2-3nm.ZrSiO₄/Cd(S_1-xSe_x) inclusion pigment was prepared by microemulsion route as ZrOCl₂, (C₂H₅)₄SiO₄, Cd(NO₃)₂·4H₂O, Se powder and Na₂S·9H₂O for raw materials in polyethylene glycol octylphenyl ether(Triton X-100)/n-hexanol/cyclohexane/water microemulsion system. NH₃·H₂O used to pH regulator and NaF used to mineralizer. The results show that, when volumn ratio of surfactant(Triton X-100), cosurfactant(n-hexanol) and oil phase(cyclohexane) is 5/6/20, the addition of mineralizer is 4%, C_Na2S is 0.4M, sintering temperature is 1150℃for 30min holding time, ZrSiO₄/Cd(S_1-xSe_x) ratio is 2 and Zr/Si ratio is 1.0/1.5, pigments with acid treatment have higher hues and inclusion ratio(45.93%). TEM analysis shows that, Cd(S_1-xSe_x) was coated by ZrSiO₄ successfully, Cd(S_1-xSe_x) is tetragon shape and the inclusion thickness is about 10nm.Results show that both hydrothermal and microemulsion method are feasible and effective on making Cd(S_1-xSe_x) to be coated by ZrSiO₄ at most before it is oxidized. The former makes good use of uncommon pressure, the later is control particle size by water core which formed by specific microreaction ware. It provides new routes for preparing ZrSiO₄/Cd(S_1-xSe_x) pigment and other inclusion pigments.