Hydrothermal synthesis and thermal change in IR reflectance of Al/W co-doped VO2 powder

Abstract Al/W co-doped VO 2 with a monoclinic structure, space group P 2 1 / c , was synthesized (hereafter, Al/W-doped VO 2 (M1)) and its thermochromic property was investigated. First, to prepare the precursor for Al/W-doped VO 2 (M1), V 2 O 5 , (NH 4 ) 10 W 12 O 41 ·5H 2 O, and AlCl 3 ·H 2 O were dispersed in a citric acid solution and then hydrothermally treated in an autoclave. Then, the Al/W-doped VO 2 (M1) powders were synthesized by heating the obtained precursor at various temperatures under an Ar gas flow. The Al/W-doped VO 2 (M1) has a monoclinic structure with space group P 2 1 / c , similar to undoped VO 2 (M1) and W-doped VO 2 (M1). The Al/W-doped VO 2 (M1) indicated that the monoclinic to tetragonal transition temperature was lowered to approximately room temperature by the Al and W doping. The Al/W-doped VO 2 (M1) had the lower optical band gap and showed a larger IR reflectance in the 800–2000 nm range, compared with W-doped VO 2 (M1) and pure VO 2 (M1).