The encapsulation efficiency of zircon pigments from robust solids to clear solutions

Purpose This paper aims to systematically demonstrate a methodology to determine the relative and absolute encapsulation efficiencies ( α Re and α Ab ) for thermally- and chemically-robust inorganic pigments, typically like ZrSiO 4 -based pigments, thereby enhancing their coloring performance. Design/methodology/approach The authors designed a route, surplus alkali-decomposition and subsequently strong-acid dissolution (SAD2) to completely decompose three classic zircon pigments (Pr–ZrSiO 4 , Fe 2 O 3 @ZrSiO 4 and CdS@ZrSiO 4 ) into clear solutions and preferably used inductively coupled plasma-optical emission spectrometry (ICP-OES) to determine the concentrations of host elements and chromophores, thereby deriving the numeric data and interrelation of α Re and α Ab . Findings Zircon pigments can be thoroughly decomposed into some dissoluble zirconate–silicate resultants by SAD2 at a ratio of the fluxing agent to pigment over 6. ICP-OES is proved more suitable than some other quantification techniques in deriving the compositional concentrations, thereby the values of α Re and α Ab , and their transformation coefficient K RA , which maintains stably within 0.8–0.9 in Fe 2 O 3 @ZrSiO 4 and CdS@ZrSiO 4 and is slightly reduced to 0.67–0.85 in Pr–ZrSiO 4 . Practical implications The SAD2 method and encapsulation efficiencies are well applicable for both zircon pigments and the other pigmental or non-pigmental inhomogeneous systems in characterizing their accurate composition. Originality/value The authors herein first proposed strict definitions for the relative and absolute encapsulation efficiencies for inorganic pigments, developed a relatively stringent methodology to determine their accurate values and interrelation.