> I didn´t find the crystalline phase
> K_6 H_2 Nb_6 O_19 .8H_2 O
> in ICSD database
There are very many phases containing niobium oxide blocks, with various
other cations and hydration states, so you may not find an exact match.
You can still use ICSD to help understand the structure if you relax the
search criteria. If you search eg for elements "K Nb6 H O" you get only 10
results, including eg K7(H Nb6O19).(H2O)10 which is already pretty close,
with one more K, one less H, plus some extra water.
You should of course remain sceptical about the precise formula that
people report, especially if they report X-ray structures of hydrogenous
heavy metal oxides :-)
If you can index the pattern determine the unit cell, you can narrow the
possibilities greatly, but again watch out for weak peaks due perhaps to
superstructure, especially for heavy metal oxides.
Alan.
______________________________________________
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
<alan.he...@neutronoptics.com> +33.476.98.41.68
http://www.NeutronOptics.com/hewat
______________________________________________
