Synthesis and infrared shielding properties of molybdenum-containing ammonium tungsten bronzes

A series of molybdenum-containing ammonium tungsten bronzes was synthesized by a solvothermal process at 200 °C for 72 h using ethylene glycol, acetic acid, ammonium tungstate and ammonium molybdate as starting materials. All the diffraction peaks of XRD for the samples synthesized with starting Mo/W (mol) = 0-0.2 could be rough indexed as a hexagonal ammonium tungsten bronze with the formula of (NH₄)_0.33WO₃, which was accompanied by a shift of the main peaks after the introduction of molybdenum and a split peak for starting Mo/W (mol) = 0.1. The nitrogen content, based on both the thermogravimetry and X-ray photoelectron spectroscopy, rose with the increase of molybdenum content. Optical properties were evaluated using Fourier transform infrared spectroscopy, which proved that the molybdenum-containing ammonium tungsten bronzes could shield infrared rays better than the sample without molybdenum. The shield efficiency was related to the content of molybdenum. The optimum starting Mo/W (mol) to obtain high infrared shielding properties was 0.1. This sample consisted of uniform rods of ca. 50 nm in diameter emerging from the agglomerates.