This paper focuses on the remarkable effects of Yb2O3 doping on the microstructure and dielectric characteristics of CaCu3Ti4O12 (CCTO). Samples were prepared by the solid phase reaction method and sintered in air at 1030 degrees C for 12 h. X-ray diffraction and X-ray photoelectron spectroscopy studies confirm that the primary phase is CCTO. Some Yb3+ ions may substitute into the Ca site at the center or zenith sites of the CCTO lattice hexahedron, while the rest of the Yb atoms may concentrate at grain boundaries. The grain size of Yb2O3-doped CCTO ceramics were examined by scanning electron microscopy and demonstrate sharp grain size reduction with Yb2O3 doping. From dielectric property measurements, the Yb2O3 doping reduces the dielectric constant of CCTO, and the dielectric loss is also reduced. (C) 2014 Elsevier Ltd. All rights reserved.