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 describedherein. The nano-crystalline powder has a high specific surface area of 55 m2 g−1 and a crystallite sizeof 15 nm. The as-prepared powder does not show any significant crystallite growth up to 700 ◦C. Theactivation energy of the crystallite growth process was calculated as 590 kJ mol−1. Dense ceramics can beobtained either after sintering at 1200 ◦C for 1 h or after two-step sintering at 1000 ◦C for 10 h. The averagegrain sizes of ceramic bodies can be tuned between 0.23 µm and 12 µm. The thermal expansion coefficientwas determined as 11.4(3)·10−6 K−1. The optical band gap varies between 2.90(5) and 2.63(3) eV. Magneticmeasurements gave a Néel temperature of 20 K. Depending on the sintering regime, the ceramic samplesreach permittivity values between 2800 and 137,000 at RT and 1 kHz.