Morphological evolution of cadmium oxide crystals showing color changes and facet-dependent conductivity behavior

Abstract

CdO stellated octahedra, octahedra, {100}-truncated octahedra, and Cd(OH)₂ hexagonal plates with respective average sizes of 147 nm, 700 nm, 2 μm, and 105 nm have been synthesized by progressively increasing the cadmium acetate and KOH amounts in ethanol and heating the mixtures in an oven set at 150 °C for just 2 h. The particle shape evolution results from free energy changes. All samples possess a high crystal quality. Cd(OH)₂ plates exhibit both sharp and broad X-ray diffraction (XRD) peaks due to their morphology. Because of the large particle size differences, these CdO crystals show distinct colors, and the obtained band gaps decrease with increasing particle sizes. The CdO {111} faces are considerably more conductive than the {100} faces. A current-rectifying effect can be observed with electrical connection made to these two crystal faces of a truncated octahedron.