Synthesis, structure and thermal stability of tellurium oxides and oxide sulfate formed from reactions in refluxing sulfuric acid

Reactions between Te, TeO2, TeCl4, TeO3 or H6TeO6 and 30-95 wt% H2SO4 were studied at temperatures up to the boiling point of the acid. Depending on t he tellurium-containing reactant, H2SO4 concentration and synthesis tempera ture, Te2O3(SO4), TeO3 or TeO3. xH(2)O (x=1.37-1.58) is obtained as the fin al product (alone or in admixture). The reaction products as well as therma lly decomposed and/or crystallized/recrystallized products of these are cha racterized by powder X-ray diffraction and thermoanalytical techniques. The findings obtained by syntheses with, and thermal decompositions of, H6TeO6 concern three crystalline [TeO3 (I), TeO3 (II) and TeO3 (III) in the prese nt notations] and one amorphous modification of TeO3, an amorphous modifica tion of H2TeO4, one crystalline and one amorphous modification of TeO3. xH( 2)O (x=1.37-1.58) and two crystalline (one with somewhat more uncertain com position) and one amorphous modification of Te2O5. The crystal structures o f TeO3 (I) and Te2O3(SO4) have been redetermined by Rietveld refinements of powder X-ray and neutron diffraction data, respectively.