Yellow-to-green colour transition effect of Pr–ZrSiO4 pigment

In this study, a Pr–ZrSiO 4 pigment was synthesised using a solid-state method with Pr 6 O 11 , ZrO 2 and SiO 2 as raw materials and H 3 BO 4 as the mineraliser. Results demonstrated that as the temperature was increased from 1100 °C to 1400 °C, the H 3 BO 4 -containing Pr 0.08 Zr 0.92 SiO 4 sample underwent a distinct colour transition from yellow (1100 °C–1200 °C) to green (1250 °C–1400 °C). By contrast, the sample without H 3 BO 4 maintained a yellow hue between 1100 °C and 1400 °C. Transmission electron microscopy analysis revealed Pr 2 Zr 2 O 7 secondary phase dispersed in ZrSiO 4 of the green powders. The added H 3 BO 4 reacted with SiO 2 to form a borosilicate glass phase that exhibited a strong adsorption capacity for lattice oxygen, resulting in the generation of oxygen vacancies in ZrSiO 4 . To maintain valence balance, Pr 4+ (yellow) converted to Pr 3+ (green) and the secondary phase Pr 2 Zr 2 O 7 was formed in ZrSiO 4 . The valence state transition of Pr ions (Pr 4+ /Pr 3+ ) was the primary reason for the colour transition. The green pigment exhibited excellent high-temperature stability, showing potential application in the ceramic industry.