Crystallite size was calculated using the Scherrer equation [19,20], D¼0.89λ/β cos θ; where λ is the wavelength of the Xray radiation (Cu Kα radiation, λ¼1.5418 Å), β is the line broadening at half of the maximum intensity and θ is the corresponding Bragg's angle.
Crystallite size increased from 7.1 nm to 10.9 nm as the heat treatment temperature was increased.