Development Of Praseodymium Doped Zircon Pigments For Ceramic Ink-jet Printing Inks

Praseodymium doped zircon pigment is the yellow pigment can be used in the ink-jet printing ceramic inks. To meet the requirement of the ceramic ink-jet printing inks, the pigments need to be milled to less than 1μm by machinery, which seriously weaken its coloring capability. In order to improve the coloring capability of praseodymium doped zircon pigments for ceramic ink-jet printing inks, the precipitation-calcination method was applied to synthesize pigments by using Zr OCl2·8H2O, Na2 Si O3·5H2O, Pr Cl3 as raw materials. The method for controlling zircon crystal grain size and increasing the amount of praseodymium ions doped in zircon lattice were explored.In this experiment, NH4 F, Li F, KF and Ca F2 were chosen as mineralizer to study the effects of mineralizers on synthesizing praseodymium doped zircon pigments at 950℃. The results showed that NH4 F was not a suitable mineralizer due to its low decomposition temperature. The particle size of the pigments prepared by Ca F2 was 15~30μm and the yellow saturation was 0.82, both of which were maxium in all samples. When Li F was used as mineralizer, the particle size of pigments could be controlled at 2~5μm, which was the minimum in all samples, but the yellow saturation was lowest. To some extent, using Li F combined with Ca F2 or KF as mineralizer could reduce the particle size of the pigments and improve the crystallinity of zirconium silicate crystals, but decrease the solubility of praseodymium ions in zirconium silicate, which weakened the coloring capability of the pigments. When Ca F2+Li F was used as mineralizer, the particle size was 10~20μm and the yellow saturation was 0.72. When KF+Li F was used as mineralizer, the particle size was 3~5μm and the yellow saturation was 0.71.By using KF+Li F and Ca F2+Li F as mineralizer, the influence of calcination temperature from 800℃ to 950℃ on synthesizing praseodymium doped zircon pigments were studied. The results showed that lowering calcination temperature could reduce the particle size from 10~20μm to 4~6μm when Ca F2+Li F was used as mineralizer, but did not affect the pigments prepared by KF+Li F. In addition, the coloring rate of pigments increased and then decreased with the calcination temperature decreasing, and a maximum reached at 860℃. Comprehensive consideration, the pigments prepared by Li F+Ca F2 performed best, its yellow saturation was up to 0.9.Four kinds of precipitation method(directive, reverse, and mixing droping method) were chosen to study the effects of precipitation process on synthesizing praseodymium doped zircon pigments. The particle size of the pigments obtained by mixing dropping method was 10~20μm, while the other three were just 4~6μm. The directive doping method resulted in the highest yellow saturation 0.97, and mixing droping method lead to the lowest one.Comprehensive experimental resulted showed that the best praseodymium doped zircon pigment was produced by directive dropping process, using Li F+Ca F2 as mineralizer, and calcining at 860℃. The mass ratio of the raw materials was as follows: Zr(OH)4+Si(OH)4︰Pr Cl3︰Li F︰Ca F2=112.25︰7.27︰0.26︰1.95. The praseodymium doped zircon pigments synthesized in the experiment was used in ceramic ink-jet printing inks. The following was the indicators of the ceramic ink: the yellow saturation(L*/b*) was 0.44, the pigments content was 45wt%, the median particle size was 0.41μm, the surface tension was 27.9 m N/m, the viscosity was 32 m Pa ? s, the density was 1.3 g/cm3, p H=7.