2.4. Materials characterization
X-ray diffraction (XRD) measurements were carried out using a D/Max-3c X-ray diffractometer with Cu Ka (l = 0.154 nm), scanning from 5 to 80 and using an operation voltage and current of 40 kV and 30 mA, respectively. Scanning electron microscopy (SEM) images and EDS date were taken on a JEOL JSM-6700 FSEM. Transmission electron microscope (TEM) images were collected by using a JEM-2100 microscope. Specimens for TEM observation were prepared by dispersing the material powder
into alcohol by an ultrasonic treatment.