Prepared samples were characterized using X-ray diffraction
(XRD) and Brunauer–Emmer–Teller (BET) surface area measurements.
The XRD patterns were collected on a Bruker diffractometer
(Germany) with graphite monochromatized CuKa radiation. The
surface areas of oxide powders were measured according to the
BET equation by N2 physisorption at 77.4 K using a Quantachrome
NOVA automated gas sorption system (Gad-Allah et al., 2008).