Effect of polyvinylpyrrolidone on morphology and structure of In2O3 nanorods by hydrothermal synthesis

Abstract Indium oxide (In 2 O 3 ) nanorods were hydrothermally synthesized from aqueous InCl 3 solution in urea with addition of polyvinylpyrrolidone (PVP) as a steric stabilizer. Indium hydroxide, In(OH) 3 , was precipitated at 60 °C and was changed into a transient InOOH phase upon calcination at ∼250 °C in air. X-ray diffractometry revealed that the existence of PVP delays the phase transformation of InOOH. Cubic-structured In 2 O 3 phase was then formed when temperature was raised to 350 °C, regardless of the PVP concentration. The In(OH) 3 phase without the PVP showed a rod-based, flower-like morphology of polycrystalline character. Minor addition of the PVP, i.e., 0.1–2 wt.%, resulted in a pronounced evolution in morphology from the three-dimensional, flower-like form to discrete, one-dimensional nanorods aligned in planar form. Both the flower-like and discrete nanorod morphologies were preserved after heat treatments at 250 and 350 °C. This reveals that the morphological change is attributable to preferential adsorption of the PVP molecules on the In(OH) 3 crystallite surface, so that the aggregate attachment responsible for the multipod growth is inhibited.