Some experts have studied the effect of the order of hydrofluoric acid addition on the optical properties of F-doped cesium tungsten bronze for nano-ceramic dispersion solution. The following figure shows UV-Vis transmittance spectra of F-doped cesium tungsten bronze prepared by using HF as fluorine source with different adding order, wherein the amount of HF added is 0.11.
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From the figure, we can see that the transmittance of F-doping cesium tungsten bronze prepared by adding HF prior to citric acid in the visible region (380-780nm) and the shielding performance in the near-infrared region (780-1100nm) are superior to F doped cesium tungsten bronze prepared by adding citric acid prior to HF. Experts say that for the order in which HF is added prior to citric acid, when tungstic acid is mixed with HF, HF is ionized to decompose F- in water, and tungstic acid is present in water as WO3•H2O. Wherein, a part of HF ionized F- replaces the O atom of WO3 to form WO3-yFy•H2O, and then, when citric acid is added, citric acid forms a stable complex with WO3-yFy•H2O. For the order of citric acid addition after HF, when tungstic acid is mixed with citric acid, the citrate and WO3 oxygen bond will form a stable complex, which may affect the incorporation of F- to some extent.
