Bismuth titanate as an infrared reflective pigment for cool roof coating

•We synthesized the bismuth titanate (BTO) using simple hydrothermal method.•BTO shows an IR reflectance value of R = 95% at a wavelength range of 700-2500 nm.•IR reflective property of BTO was compared with conventional infrared reflective white pigment, TiO2.•BTO shows a thermal difference of almost 10 °C during thermal study.•BTO pigment will be a potential “cool pigment” with high IR reflectance property for energy saving application.

A pale-yellow color nano pigment Bi4Ti3O12 (BTO) with impressive infrared (IR) reflectance (R = 95%) was synthesized using a simple hydrothermal method and characterized its crystalline nature, structural property, morphology and optical properties using X-ray diffraction technique (XRD), Raman spectroscopy, Fourier Transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV-Vis-NIR spectrophotometer. The Near infrared (NIR) reflectance was measured using UV-Vis-NIR diffuse reflectance spectrophotometer at a wavelength range of 700-2500 nm. The band gap of the synthesized BTO nano pigment increases from 2.74 to 3.05 eV by increasing the calcination temperature from 600 °C to 800 °C. For comparison study, the IR reflectance property and the thermal performance of synthesized BTO nano pigment was compared with the conventional infrared reflective white pigment TiO2. The BTO nano pigment shows higher NIR reflectance property and better thermal performance than the TiO2 pigment. The potential application of the BTO nano pigment as the “cool pigment” was also demonstrated by coating on to the steel substrate for the energy saving application.