A novel pyrophosphate BaCr2(P2O7)2 as green pigment with high NIR solar reflectance and durable chemical stability

• A novel green pyrophosphate pigment BaCr2(P2O7)2 was firstly synthesized.
• Cr3+ ion acts as a chromophore cation, enhancing the green color greatly.
• A significantly high solar reflectance of 90% indicates its cooling function.
• Durable chemical stability were found in BaCr2(P2O7)2 and ceramics.

A novel pyrophosphate BaCr2(P2O7)2 was synthesized by the conventional solid-state reaction. The X-ray diffraction (XRD), FTIR spectrum, scanning electron microscopy (SEM) and ultraviolet–visible (UV–Vis) near infrared (NIR) reflectance spectra were applied to characterize the powders. The refractive indexes and nature of the VB and CB were determined. The structure, color properties and application were investigated. The results reveal that the anomalist bodies with smooth surfaces were obtained at 1200 °C with a mean size of 3 μm. A high reflectance peak at 535 nm was observed in the visible region, which is associated with the brilliant and deep green color of this pigment. With all the acids, alkali and deionized water treatment, the polycrystalline pigment BaCr2(P2O7)2 was found to be durable in chemical stability. The significantly high NIR solar reflectance of BaCr2(P2O7)2 is 90.0%, a higher cooling ability, so it has been selected to be tested as cool green pigment in ceramics. Moreover, this novel pyrophosphate pigment has great potential as cool pigment for surface coating applications.

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