Increase in depolarization temperature and improvement in ferroelectric properties by V5+ doping in lead-free 0.94(Na0.50Bi0.50)TiO3-0.06BaTiO3 ceramics

A detailed study was carried out to investigate the effects of poling on structure, vibrational, dielectric, and ferroelectric properties of donor-doped (V5+ at Ti4+-site) lead-free Na0.47Bi0.47Ba0.06Ti(1-x)VxO3, (x = 0, 0.01, and 0.03) ceramics fabricated via a modified sol-gel method. Rietveld refinement of synchrotron radiation source powder x-ray diffraction data showed that unpoled samples are in rhombohedral R3c phase whereas poled samples showed a mix rhombohedral R3c and tetragonal P4mm phases at ambient temperature, due to a long-range order established in lattice system after poling. V+5 doping increases the rhombohedral distortion in unpoled and poled samples while it reduces the tetragonality in poled samples. Vibrational study revealed that unpoled samples have more lattice disorder compared to poled samples. X-ray absorption near edge spectroscopy measurement confirmed that Ti and V are in 4+ and 5+ oxidation states, respectively, for all poled and unpoled samples. The average grain size was found to decrease from 5.6 +/- 0.5 mu m for x = 0 to 1.0 +/- 0.2 mu m for x = 0.03. Depolarization temperature was found to increase significantly in poled samples from similar to 104 degrees C for undoped sample to 150 degrees C for the sample with 1% vanadium substitution. Drastic improvements in ferroelectric and dielectric properties are explained in terms of structural changes. High remnant polarization P-r similar to 31.4 mu C/cm(2) and moderately low coercive field E-c similar to 20 kV/cm have been observed at an applied electric field of similar to 35 kV/cm for the sample with 1% vanadium substitution which makes it an attractive candidate for ferroelectric applications. Published by AIP Publishing.