X-ray diffraction analysis (XRD)

Undoped and doped SnO2 samples were examined by XRD, the average crystallite sizes were estimated from the Debye-Scherrer equation [382].

where D is the crystallite size, K is the Sherrer's constant (0.9), λ is the λ of Cu K𝛼 radiation (1.5418 Å), θ is the diffraction (Bragg's) angle, and 𝛽 is the full width at half maximum (FWHM).

The lattice parameters 'a' and 'c' for the tetragonal structure (a = b  c,  =  =  = 90 º) can be calculated by the following expression [383],

where h, k and l are the Miller indices but variables (a and c) are the lattice constants.

The unit cell volume of the products is given by the formula.

The XRD analysis for SnO2/I Nps synthesized by sol-gel were done by placing the powder on the special glass provided through Miniflex 600 diffractometer

Each powder was prepared for XRD analysis using the technique explained in section 3.7.1.1, the powder was spread on the glass holder and placed on the magnetic recognition and the preparation method loaded. The XRD analysis was obtained after turning on the detector in continuous scan mode operated at 30 kV and a current of 15

4.2 Characterization of the synthesis materials 117 mA. Diffractograms of the powder was recorded in 2 θ scan configuration, in the range of 10-80°2 θ range at steps of 0.02°.

The XRD patterns of undoped SnO2, doped SnO2/I 0.2 wt. % and SnO2/I 1.0 wt. % samples synthesized by sol-gel process with the results are shown in Figure 11.

Figure 11: XRD patterns of undoped SnO2, SnO2/I 0.2 wt. % and SnO2/I 1.0 wt. % Nps synthesized by sol-gel process

Figure 11 indicates the presence of ten peaks which correspond to the SnO2 crystal planes of 110, 101, 200, 111, 211, 220, 002, 310, 112, and 301 respectively. The results in Figure 11 matched the standard XRD file of SnO2 (JCPDS-# 41-1445) (JCPDS abbreviation stands for Joint Committee on Powder Diffraction Standards) [161, 336, 338, 384-386], which are regarded as an attributive indication of the rutile SnO2

structure.

The calculated crystallite sizes of the undoped, SnO2/I 0.2 wt. %, and SnO2/I 1.0 wt. % in the Figure were estimated by the FWHM of the most intense peak (110) using the Debye-Scherrer equation. The obtained SnO2 crystallite sizes followed the well-known trend of crystallite size reduction, when the control SnO2 showed 8.4 nm. But when

SnO2 was doped with I, the crystallite size drastically reduced (SnO2/I 0.2 wt. % it decreased to 8.0 nm; and 2.5 nm for SnO2/I 1.0 wt. %).

Figure 12: XRD patterns of undoped SnO2, SnO2/Gd 0.6 wt. % and SnO2/Sb 0.6 wt. % Nps synthesized by sol-gel method.

SnO2/Gd 0.6 wt. % and SnO2/Sb 0.6 wt. % were both compared with undoped SnO2

Nps. All the metals were synthesized by sol-gel and the powder were kept away of light and humid in a desiccator until characterized. The powder of each doped and undoped Nps was spread separately on the glass for the XRD measurement after the glass was cleaned and dried in the oven.

In Figure 12 the XRD patterns showed the undoped SnO2,SnO2/Gd 0.6 wt. %, and with SnO2/Sb 0.6 wt. %. The crystallinity of each of the powder was characterized alone; no observable changes could be seen in the patterns between them.

In Figure 12 the obtained SnO2 crystallite sizes followed the well-known trend of crystallite size reduction as in previous Figures, although, the control SnO2 showed 8.4 nm, but when the Gd was doped with SnO2 as SnO2/Gd 0.6 wt. % the crystallite size

4.2 Characterization of the synthesis materials 119 severely decreased to 3.2 nm. Again the crystallite size continued to significantly reduce down until it reached 1.8 nm for SnO2/Sb 0.6 wt. %.

Figure 13: X-ray patterns of undoped SnO2, SnO2/Gd 0.6 wt. %, SnO2/La 0.6 wt. % SnO2/Nd 0.6 wt. % and SnO2/Ce 0.6 wt. % Nps synthesized by sol-gel process.

In another analysis, all RE metals were compared with the control such as the undoped SnO2, SnO2/Gd 0.6 wt. %, SnO2/La 0.6 wt. % SnO2/Nd 0.6 wt. % and SnO2/Ce 0.6 wt.

%. Each of these samples spread alone on each glass holder provided for XRD as it described before and put in the XRD. The XRD patterns in Figure 13 indicated that the diffraction angles at 2 θ =26.3°, 33.6º, 37.62º, 51.68º, 54.46º, 57.7º, 61.60º, 65º, 65.62º, that can be assigned to 110, 101, 200, 211, 220, 002, 310, 112, and 301 respectively, matched with the standard XRD file of the rutile phase of SnO2 [161, 336, 338, 384-386].

No much difference could be gained in the XRD patterns between them and the previous patterns in Figure 11 and 12.

Although the previous Figures 11 and 12 followed the well-known trend of crystallite size reduction, as it followed and SnO2 showed 8.4 nm, while Ce doped SnO2 as (SnO2/Ce 0.6 wt. %) decreased to 5.5 nm. When Nd was doped to SnO2 as SnO2/Nd 0.6 wt. % notably reduced to 4.1nm, on the other hand, as La was doped with SnO2 the crystallite size extensively continued to reduce to 3.4 nm. With Sb doped SnO2 it appreciably lessen to 1.8 nm for SnO2/Sb 0.6 wt. %.

Figure 14: XRD patterns of undoped SnO2, SnO2/Sb 0.2 wt. %, SnO2/Sb 0.4 wt. %, and SnO2/Sb 0.6 wt.

% Nps synthesized by sol-gel method.

The characterization of SnO2 with different dopant ions, such as undoped SnO2, SnO2/Sb 0.2 wt. %, SnO2/Sb 0.4 wt. %, and SnO2/Sb 0.6 wt. % Nps was also analysed.

Figure 14 indicates the XRD pattern of undoped SnO2 sample showed the presence of peaks as (110), (101), (200), (211) and (112) respectively. Matched with the standard XRD file of SnO2 (JCPDS-# 41-1445) [161, 336, 338, 384-386], regarded as an attributive indication of rutile SnO2 structure. The doped samples at differently SnO2/Sb concentrations of 0.2, 0.4, and 0.6 wt. % showed no substantial differences in XRD

4.2 Characterization of the synthesis materials 121 patterns compared to the undoped SnO2. Again, Figure 14 showed that the crystalline size decreased with the increasing Sb doping wt. % onto SnO2.