Novel NaFeTiO4 cool pigment with high-infrared reflectance and low thermal conductivity

• A facile molten salt method was used to successfully synthesize colored sodium iron titanate pigment. • The growth mechanism of sodium iron titanate whiskers was proposed. • Sodium iron titanate has a high average near-infrared reflectivity. • The obtained whiskers have good thermal stability in the temperature range from room temperature to 900 °C. • The sodium iron titanate whiskes can be expected to be an excellent cold pigments with low thermal conductivity. High near-infrared (NIR) reflectivity and low thermal conductivity are desired in cooling pigments used in exterior coating of buildings. In this work, brown-red whisker-like sodium iron titanate pigment were synthesized using Na 2 CO 3 , TiO(OH) 2 and Fe 2 O 3 as the raw materials and NaCl as the flux. We explored the optimal preparation conditions of sodium iron titanate, and investigated the near-infrared reflection characteristics, thermal conductivity and thermal stability of sodium iron titanate. The results show that single-phase sodium iron titanate whiskers can be obtained after calcination at 900 °C for 4 h. The growth of sodium iron titanate whiskers conforms to the series-parallel growth mechanism, and the well-developed sodium iron titanate whisker has a high average reflectivity (81.43%) in the near-infrared band of 780–2500 nm. The sodium iron titanate whisker has a low thermal conductivity (0.136 W/mK, at room temperature), which is mainly attributed to the inherent tunnel crystalline structure. In addition, sodium iron titanate has good thermal stability in the temperature range from room temperature to 900 °C. The present brown-red NaFeTiO 4 whisker is expected to be a candidate pigment for building energy conservation.