Ian is correct when he says it is improved by annealing. In this case, heating
it to 1200 deg C for 3 days reduced the peak widths from 0.16 to 0.07 deg two
theta.
Martin Vickers
Dept. of Crystallography
Birkbeck College
Malet Street
London WC1E 7HX
P.S. I do not advocate "teaching ones grandmother to suck eggs" but don't
expect the Inel to resolve the peaks as well as this.