Precipitation synthesis of Cr3+-doped ZrSiO4 green pigment: Phase evolution, crystal-field and colorimetric insights

A cost-effective and environmentally friendly precipitation method involving the in-situ formation of NaCl during the precipitation process has been successfully adapted for the synthesis of Cr 3+ -doped ZrSiO 4 green pigment for the first time. The addition of a small amount of NaF to the SiO 2 –NaOH–ZrOCl 2 –CrCl 3 –H 2 O system, followed by stirring of the boiling mixture for 1 h, leads to the formation of an intermediate phase that crystallized into zircon after heat treatment at 900 °C for 1 h. Optimization of the precursor composition enabled the formation of zircon as the dominant phase (>90%) in the final product. The absorption spectrum of the optimized Zr 0.9 Cr 0.1 SiO 4 pigment exhibits characteristic Cr 3+ d–d transitions. Crystal-field parameters derived from the absorption bands placed Cr 3+ ions in the intermediate-to-strong crystal-field regime, consistent with the observed coexistence of sharp-line and broadband emission. Elemental analysis revealed a solubility limit for Cr 3+ incorporation into the zircon lattice corresponding to an actual composition of Zr 0.941 Cr 0.059 SiO 4 , in good agreement with occupancy factors obtained from Rietveld refinement. The synthesized pigment exhibits a distinctive green coloration, high thermal and chemical stability, and excellent glaze performance, making it a promising candidate for ceramic, artistic, and decorative applications.