Study On The Synthesis And Alkali Resistance Of The Green Uvarovite Colorants

The alkali resistance of traditional green ceramic colorants and pigments were preliminarily explored in this research for the purpose of improving alkali resistance of ceramic colorant. The result showed that the alkali resistance of ceramic colorants were better than that of pigments. Colorant, as a significant component of the pigment, had pivotal influence on improving alkali resistance of pigment. Consequently, taking alkali resistance as a main consideration of this reseatch, the coloration mechanism of victoria green colorant was systematically investigated in this research as well as the influence of various species of mineralizing agents and their adding amount, molar ratios of Ca:Si amd Ca:Cr, metal cation ion doping and soaking time on the color, composition, structure and alkali resistance of colorant.Uvarovite victoria green colorant was synthesized by means of solid-phase reaction. This thesis discussed the influence of 6 mineralizing agents of CaF2, CaCl2, NaF, H3BO3, Na2SiF6, KNO3 and their various adding amounts, molar ratios of Ca:Si and Ca:Cr of parent uvarovite, A and B site doping with Ba2+ and Al3+ respectively, and various soaking time on the color and alkali resistance of prepared samples. Colorimetric analysis of samples before and after alkali resistance was carried out to characterize the coloration and colorimetric parameters. XRD, FESEM, EDS, Grain size analysis and Fourier infrared analysis were also employed to characterize the samples.The experimental results showed that pure pure Ca3Cr2(SiO4)3, with the best coloration and a* value of -22.42, could be synthesized using CaF2 as mineralizin g agent with adding amount of 6wt%. Sample with maximum alkali resistance of 95.67% and a* value of -24.15 could be obtained when ration of Ca:Si set at 1: 1 and calcinated at 1160? for 6 hours, and the prepared colorant were well-grow n uvarovite rhombus dodecahedron crystals with particle size of about 6?7?m. Sa mples with excellent a* valure of -25.32 was prepared when ratio of Ca:Cr set at 0.6:1 and calcinated at 1160? for 6 hours, the uvarovite crystals were well-deve loped and well-dispersed with particles size of 9?10?m. The resultant colorant ha d the maximum alkali resistance of 96.93%. Regularly-shapped well-dispersed and well-developed uvarovite rhombus dodecahedron crystals of 14?15?m were prepar ed when Ca:Ba molar ration was set at 0.95:0.05 and calcinated at 1160? for 2 hours. The maximun alkali resistanc of the resultant colorant was 96.75%. Sample swith the best a* value of -29.18 and maximum alkali resistance of 99.30% were synt-hisized when Cr:Al molar ratio was set at 0.95:0.05 and calcinated at 1160 ? for 2 hours, and the uvarovite crystals of 14?15?m were further developed.