Structural characterizations and electrical conduction mechanism of CaBi₂Nb₂O₉ single-phase nanocrystallites synthesized via sucrose-assisted sol–gel combustion method

A pure phase of nanocrystalline ferroelectric of calcium bismuth niobate (CaBi₂Nb₂O₉, CBNO) has been synthesized via sucrose-assisted sol–gel combustion method. It was prepared using calcium nitrate, bismuth nitrate pentahydrate, and niobium pentoxide in the presence of sucrose. The prepared CBNO powder ceramics were calcined at different temperatures to ensure formation of single-phasic nanocrystallites. X-ray diffraction, selected area electron diffraction, and high-resolution transmission electron microscopy were employed to study the structural properties and to verify the single-phase nanocrystalline formation, which was found at calcining temperature of 1200 °C. Then, thermogravimetric analysis, differential scanning calorimetry, and Fourier-transform infrared were utilized to characterize thermal stability and functional groups of the prepared pure orthorhombic phase of CBNO nanocrystalline ceramics. Moreover, electrical properties of the prepared CBNO powder were rigorously investigated in air with frequencies and temperatures ranges of 1 kHz–8 MHz and 300–1000 °C, respectively. The electrical results were interpreted depending on the bipolaron and single-polaron-correlated barrier height mechanisms. The prepared pure orthorhombic phase possesses high stability and has Curie temperature at about 932 °C, which makes this material promising for working as a resonator for high-temperature operations, for example, automotive engine control application.