The synthesis of Ce1−xLnxO2−y (Ln=Pr, Sm, Gd, Tb) nanocubes by hydrothermal methods

Abstract

The synthesis of Ce1−xLnxO2−y (Ln=Pr, Sm, Gd, Tb) cube shape nanoparticles by hydrothermal and microwave assisted hydrothermal method is described. The effect of the Ln doping on morphology and the phase composition of ceria was studied by XRD, electron microscopy and Raman spectroscopy. Up to certain Ln content x=xm (depending on Ln), the hydrothermal treatment at 220°C for 24h produces nanocubes of the mixed Ce–Ln oxide, while at higher Ln content rod-like particles of Ln(OH)3 occur as a second phase. Morphology and size distribution of ceria nanocubes depend on the kind and amount of Ln dopant. Generally, the size distribution of ceria nanocubes narrows for x≥0.2, with simultaneous rounding of the cubes׳ edges and corners. Unexpectedly, noticeable number of very large, well-develop ceria nanocubes (up to 300nm) formed for small addition of Gd or Sm (x<0.1). The microwave assisted hydrothermal method enables the synthesis of the Ce1−xLnxO2−y nanocubes at significantly shorter time (3h), but with higher content of the mixed (Ln,Ce)(OH)3 hydroxide as a second phase. The effect of the lanthanide doping on mechanism of formation of Ce1−xLnxO2−y nanocubes is discussed within the framework of the oriented attachment model.