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2. EXPERIMENTAL DETAILS 
For the synthesis of ZnO Nanopowder by a sol-gel method, (13g) of Zinc acetate dehydrate Zn (CH3COO) 
2
.2H
2
O 
was dissolved in methanol solution (0.6M) under continuous stirring. The mixed solution was stirred with a 
magnetic stirrer at 80
o
C for 2 hours to form a transparent sol; its pH was adjusted with ammonia between 9 and 11. 
After adjusting the pH by using pH Meter, the sol was dried at 100 
o
C for 1 hour, and then the temperature was 
increased up to 150 
o 
C until gelation occurred. The white precipitate formed after the evaporation was filtered, 
washed with methanol several times, dried at 200 
o 
C and then calcined in an oven at 500 
o 
C for 3 hours. The 
temperature of the dried powder was increased at the rate of 3
o
C/min to attain the required temperature (500
o
C). 
Finally, zinc oxide nanoparticle powders were weighed (4g) and pressed into 20 mm diameter and 2 mm height 
discs by 150 MPa pressure using a hydraulic press (Figure1). 
Fig.1 ZnO based varistor. 
The synthesized sample was characterized for their structure by X-ray diffraction (XRDLEYBOLD-TYPE1.03 
diffraction) with CuKα radiation (λ = 1.5148 Å) as incident radiation. The morphological surface of the ZnO 
nanoparticles was studied from AFM (easyScan2 FlexAFM- SAMPLE STAGE). The sintered sample at temperature 
1050 °C are covered by silver paste and heated at 600°C for 10 min for measuring the electrical characteristics (I-V) 
by using V-I source/measuring unit MEGOHMMETER-M1500P 
3. RESULTS AND DISCUSSION 
3.1. XRD
X-ray diffraction (XRD) at 40Kv was used to estimate the crystalline sizes. The intensity data were collected over a 
2θ range of 20-80
o
. Figure (2) shows the XRD morphology of prepared ZnO nanoparticles at 500 
o
C for 3 hours. In 
our case all the diffraction peaks at angles (2θ
o
) of 31.78°, 33.9°, 36.8°, 47.63°, 56.67°, 62.94° and 67.98°and
correspond to the reflection from (100), (002), (101), (102), (110), (103), (112) crystal planes of the hexagonal 
wurtzite zinc oxide structure (Figure3). all the diffraction peaks agreed with the reported JCPDS data[11], and no 
characteristic peaks were observed other than ZnO. 
 
Khalaf AL ABDULLAH, Sahar AWDE/ Energy Procedia 00 (2017) 000–000 
3 
Fig.2. XRD pattern of ZnO nanoparticles annealed at 500 
o 
C for 3 hour Fig.3. The wurtzite structure model of ZnO 
The average grain size of ZnO nanoparticles was around 12 nm using the diffraction intensity of ( 101 ) peak from 
Debye -Sherrer equation [12,13]:
…………………….(1) 
where, 0.94 is the shape factor, λ is the X-ray wavelength (1.5148°A),β is the full width at half the maximum 
intensity (FWHM) in radians, and θ is the diffraction Bragg angle. The detailed analysis of the XRD and the 
assignments of various reflections are given in the Table1. 
Table 1.Analysis of XRD and the assignments of various reflections of ZnO
Hkl 
2θ° 
FWHM(deg) 
D(nm) 
100 
31.8° 
0.50 
16.5 
002 
101 
102 
103 
110 
112 
33.9°
36.8°
47.9°
57.9° 
62.8°
68.8° 
0.45 
0.65 
0.4 
0.3 
0.5 
0.6 
18.47 
12.89 
21.75 
29 
17.4 
14.5