where I(hkl) are the measured intensities of the (hkl)
reflection, Io(hkl) powder diffraction intensities according
to the JCPDS card no 46-1212 and n is the number
of reflections used in the calculation. The indices are
given in hexagonal system and, consequently, four axes
(hkil) are used. The index i is the reciprocal of the sum of
first two i.e. (h + k) = i. The following (hkil) reflections
were used: ð1 0 1 2Þ, ð1 01 4Þ, ð1 12 0Þ, ð1 12 3Þ, ð1 12 6Þ
and ð3 03 0Þ. The ð2 0 2 4Þ reflection, which is the
second-order reflection of ð1 01 2Þ, was omitted from
the calculations.