Effect of annealing temperature on the crystallography, particle size and thermopower of bulk ZnO

The precursor of nanopowder ZnO was synthesized by direct precipitation method and compacted to bulk samples. The bulk ZnO was annealed by furnace at temperature range of 400–650 °C in air for 30 min. The crystallography of precursor and bulk powder of ZnO was analyzed by the X-ray diffraction (XRD) and scanning electron microscopy (SEM) and obtained the hexagonal crystal structure, mean lattice parameters of a = b = 3.2478 Å and c = 5.2037 Å and unit cell volume of 47.53 Å3. The particle size was investigated by SEM and evaluated by XRD results about 76.28 nm and bulk density of 3494.14 kg m−3. The thermopower was measured by steady state method and obtained highest value of −92.99 μV K−1 at room temperature for annealing temperature of 550 °C.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Annealing at 400–650°C had effects of crystal structure, nanoparticle and thermopower of bulk ZnO.