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

Abstract

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 Na2CO3, TiO(OH)2 and Fe2O3 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 NaFeTiO4 whisker is expected to be a candidate pigment for building energy conservation.