Investigations of BaFe0.5Nb0.5O3 nano powders prepared by a low temperature aqueous synthesis and resulting ceramics

A facile method to prepare nanoscaled BaFe0.5Nb0.5O3 via synthesis in boiling NaOH solution is described herein. The nano-crystalline powder has a high specific surface area of 55m2g−1 and a crystallite size of 15nm. The as-prepared powder does not show any significant crystallite growth up to 700°C. The activation energy of the crystallite growth process was calculated as 590kJmol−1. Dense ceramics can be obtained either after sintering at 1200°C for 1h or after two-step sintering at 1000°C for 10h. The average grain sizes of ceramic bodies can be tuned between 0.23μm and 12μm. The thermal expansion coefficient was determined as 11.4(3)·10−6K−1. The optical band gap varies between 2.90(5) and 2.63(3)eV. Magnetic measurements gave a Néel temperature of 20K. Depending on the sintering regime, the ceramic samples reach permittivity values between 2800 and 137,000 at RT and 1kHz.