> > About Ba2TeO5, it is said that it is isomorphous with Ba2WO5 and Sr2WO5. > Ba2WO5 belongs to the K2VO2F3 structure type... >
> BTW Armel, Ba2WO5 itself has been determined according to Google: A more accessible and interesting reference is for the isomorphous Ba2ReO5: "An investigation of the low oxidation state chemistry of rhenium in the Ba O - Re - Re2 O7 phase diagram". *Cheetham, A.K.;Thomas, D.M. (1987) Journal of Solid State Chemistry (1987) 71, 61-69 <http://www.sciencedirect.com/science/article/pii/0022459687901423>* Whether or not these Pnma structures are indeed isomorphous with the supposed P41212 structure of Ba2TeO5 is open. I assume that the information on Ba2TeO5 comes from the PDF and is based on x-ray powder diffraction indexing. If so, that's not a very reliable source for the stoichiometry of heavy metal oxides. The structure of Ba2ReO5 was determined by neutron powder diffraction. But if we speculate as well for the other unknown, pbcn (60) Ba2TeO4, it could be isomorphous with pnma (62) Ba2 (Cr,Si,Co) O4 and if so a neutron structure is again available: "Crystal structures and magnetic properties of (CrO4)(4-) containing oxides: Sr2CrO4 ,Ba2CrO4 ,Ba3CrO5". *Liu, G.;Greedan, J.E.;Gong, W. (1993) Journal of Solid State Chemistry 105, 78-91 <http://www.sciencedirect.com/science/article/pii/S0022459683711953>* Whether or not any of this is useful to Rachid is doubtful. It would be best for him to try to prepare a sample without impurity phases. The chemistry of mixed valence heavy metal oxides is difficult enough, even with neutron diffraction let alone x-ray powder diffraction, without having poorly characterised impurity phases to contend with. Alan ______________________________________________ * Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE * <alan.he...@neutronoptics.com> +33.476.98.41.68 http://www.NeutronOptics.com/hewat ______________________________________________
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