According to Rietveld refinements of the Xray diffraction data, the highest purity sample contained 89.5 ± 0.3 wt% Ni 4 V 3 O 10 for the ball milling technique and 86.8 ± 0.1 wt% Ni 4 V 3 O 10 for the hand grinding technique. Neutron powder diffraction data revealed that ball milling introduced an Fe 2 O 3 impurity of about 0.03 wt% in the product. A small peak for this impurity could also be found in the 11-BM X-ray diffraction pattern at d = 2.50 Å (Fig. ). The other expected prominent structural peaks of Fe 2 O 3 at d = 2.69 and 3.67 Å overlap with peaks of other phases and thus were not distinguishable in the data. Qualitative XRF confirmed that Fe was present in ball-milled samples but absent in handground samples.