2016. 57, 1 UDC 541.67 EFFECTS OF A DONOR CONCENTRATION ON THE STRUCTURE OF Nb-DOPED NANO-SIZED BaTiO3 POWDERS PREPARED BY MICROWAVE-HYDROTHERMAL SYNTHESIS METHODS A. Khanfekr, M.Tamizifar, R. Naghizadeh Department of Metallurgical and Materials Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran E-mail: khanfekr@iust.ac.ir Revised December, 28, 2014 BaTi1–xNbxO3 compounds (with x = 0.00, 0.01, 0.03, 0.06, and 0.09) are synthesized by the microwave-hydrothermal (MH) method. <...> The donor concentration effect on the structural properties is investigated. <...> The new MH method is used instead of the previous solid state reaction for the BaTiO3+Nb2O3 system. <...> In the MH process, as the niobium incorporation rate increases, the particle growth substantially slows down. <...> The synthesis of Nb-doped BaTiO3 is investigated under the MH conditions subjected to 150 C for only 2 h using C16H36O4Ti (tetra-n-butyl orthotitanate), Ba(OH)28H2O, and NbCl5 as Ba, Ti, and Nb sources respectively. <...> For the phase evolution studies, X-ray diffraction patterns are analyzed and Raman spectroscopy is performed. <...> The transmission electron microscope and the field emission scanning electron microscope images are taken for the detailed analysis of the grain size, surface, and morphology of the compound. <...> Their mixed conductivity by both ion and electron migration and their high nonstoichiometric composition have resulted based on the applications of this group of materials in the areas such as electrochemistry [ 1, 2 ], oxygen separation membranes [ 3 ], chemical sensors for the detection of humidity [ 4 ], alcohol [ 5 ], and gases such as oxygen [ 6 ], hydrocarbon [ 7 ] and nitric oxide [ 8 ] from three decades ago until the present time. <...> As the result of a strong dependence of the ferroelectric properties on the grain size and compositional aspects, the microstructural control has become very important [ 9 ]. <...> The doping of barium titanate (BT) ceramics by aliovalent dopants causes many changes in the properties of the materials such as conductivity, especially at high temperatures, morphology, dielectric behavior, and so on. <...> In the present paper regarding the solid state method, the results of studies with respect to processing Nb-doped BaTiO3 are reported. <...> Specifically, it is shown that Nb ions can be incorporated into the BaTiO3 lattice in a narrow temperature <...>