Silver antimonates with pyrochlore-like structure prepared by thermal treatment of silver proton-exchanged antimonic acid: Formation process and structural characterization

Silver proton-exchanged antimonic acids, with pyrochlore-type structure and composition of H2-xAgxSb2O6. nH(2)O,(0 < x <2) have been obtained, and the y have been used as precursors for preparing silver antimonates The ionic c onductivity of the silver proton-exchanged samples as prepared is dominated by proton motion, which is clearly affected by the water content. The form ation reaction of silver antimonates has been followed by thermal analysis, mass spectrometry, X-ray diffraction, etc. Four regions can be distinguish ed: (i) from room temperature to 400 degrees C, weakly bonded water and pro tons are removed as water; (ii) from 400 to. 600. degrees C, oxygen is remo ved from the pyrochlore framework leading to reduction of some Sb5+ to Sb3; (III) from 600 to 950 degrees C, thermally stable silver antimonates with pyrochlore-like structure are formed with the amount of Sb3+ decreasing on increasing the silver content; and (iv) above 950 degrees C, the silver an timonates decompose giving beta-Sb2O4, which sublimates, and metallic silve r. Crystal structure of the silver antimonates has been analyzed; by X-ray diffraction; According to the Rietveld refinement, Ag+ and Sb3+ are placed in the channels of the pyrochlore-like structure.