Boron and praseodymium doped bismuth oxide nanocomposites were prepared through polymeric precursor technique. The nanocomposites were then sintered to identify the changes in the microstructures of the nanocomposites. The microstructural properties of the nanocomposites were investigated by means of Brunauer-Emmett-Teller nitrogen adsorption, a Scanning Electron Microscope, a Fourier Transform Infrared Spectrometer, and an X-Ray Diffractometer. The Fourier Transform Infrared Spectra of nanocomposites was attested from the presence of boron, praseodymium, and bismuth oxides. According to the X-Ray Diffractometer results, beta-bismuth oxide was formed after calcination. Moreover, sintering affected on the crystalline structure of the boron undoped nanocomposite. The sintered boron doped nanocomposite was mainly consisted of the hexagonal bismuth praseodymium oxide while the beta-bismuth oxide phase was dominant for the sintered boron doped nanocomposite. The Scanning Electron Microscope micrographs of the nanocomposites showed the plate-like structures. The surface areas of the nanocomposites were decreased because of sintering in accordance with the Brunauer-Emmett-Teller results. (C) 2018 Elsevier B.V. All rights reserved.