Abstract
According to the proposed quantitative chemical and X-ray analyses, the composition of the ‘tungsten blue oxides’ (TBO) investigated varies over a very broad spectrum, depending on the temperature, atmosphere, and speed and also on the actual manufacturing process of the ammonium paratungstate tetrahydrate (APT·4H2O) reduction. In addition to crystalline compounds {hexagonal tunsten bronze (HTB), WO3, W20O58, and W18O49} the industrially produced TBO contains 30–55% of X-ray-amorphous fraction.APT·4H2O changes in a stream of dry hydrogen at 130°C into the phase APT·∼2H2O, observed for the first time. The intermediate X-ray-amorphous phases ranging from 250 to 350°C are the starting pool not only for HTB but also for the crystalline tungsten oxides.The HTB-containing TBO powders display a considerable potassium incorporation via the cation exchange of H+ being replaced by K+.The solid-state high-resolution 1H NMR investigation of TBO allows a distinction to be made between different proton-containing species.
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