X-ray diffraction (XRD) analysis

The X-ray diffraction is a very important technique
that has been used to address all issues                                                                                             
related to the crystal of solids, including lattice constant and
identification the geometry of unknown materials. The XRD pattern of the
prepared ZnO, Co- doped, and Ni- doped ZnO are given in Figure 5(a,b,and c).
The XRD of the ZnO shows diffraction peak at 2


, 34.45

, 36.28

, 47.57

,and 56.62

 which can be indexed to (100),(002), (101)
(102) (110) and (200) crystal plane respectively, the position of these peak
indicate the formation of hexagonal wurtzite structure which are very agreement
with standard JCPDS(NO-36-1451)(2157-7439). Similar characteristic peaks and
assigned lattice plane were observed by some other research 15.XRD pattern of
Co-doped ZnO consists of diffraction peaks located in 2? = 19.7785, 23.4242,
27.5667, 28.9447, 33.2112, 33.6991, 48.5689, 59.1846, and 69.5614 respectively as
shown in Fig. 5(b) . No peaks associated with Co was detected in the XRD
pattern indicating that Co2+ ions have substitutionally replaced the
Zn2+ ions  16. Figure 5(c)
presented the XRD pattern of Ni-doped ZnO
the pattern show peaks in (100) and (101). No signals of the metallic Zn are
detected by XRD. Also, there is no peak attributed to Ni, suggesting that the
Ni+2 ion may be doped into ZnO  17  From results it was evident that incorporation
of  Co and Ni into ZnO lattice improves
crystalline quality. The average crystalline size is
calculated using Debye–Scherrer equation 18,



 D = is the
average crystalline size of the nanoparticles,

k = is geometric factor (0.94),

?= is the wavelength of X-ray radiation source

 = is the angular (full-width at half maximum)
FWHM  of the XRD peak at the diffraction

The calculated average crystalline size of the
undoped,Co-doped,and Nidoped ZnO are about (    ) nm, respectively.