Structural phase transitions in Ti-doped Bi 1-xNd xFeO 3 ceramics

Abstract

Recently, it was demonstrated that donor doping with Ti on the B-site significantly reduces the conductivity in Bi 0.85Nd 0.15FeO 3 ceramics Kalantari, Adv. Funct. Mater. 21, 3737 (2011). In this contribution, the phase transitions as a function of Nd concentration are investigated in 3 Ti doped Bi 1-xNd xFeO 3 ceramics. Paraelectric (PE) to ferroelectric (FE) transitions were observed for compositions with x 0.125 which manifested themselves as peaks in permittivity. In contrast, PE to antiferroelectric (AFE) transitions for 0.15 x 0.20 gave rise to a step-like change in the permittivity with x 0.25 exhibiting no sharp anomalies and remaining PE until room temperature. The large volume change at the PE to FE/AFE transitions, reported by Levin and co-workers Phys. Rev. B 81, 020103 (2011) and observed here by dilatometry, coupled with their first-order character constrain the transitions to occur uniformly throughout the material in an avalanche-like manner. Hence, the anomalies in DSC, permittivity and thermal expansion occur over a commensurately narrow temperature interval. However, despite the large volume change and eye-catching anomalies in DSC, the latent heats for the transitions in Ti-doped Bi 1-xNd xFeO 3 are similar to Pb(Zr,Ti)O 3 (1-3 kJ/mol) with each an order of magnitude greater than BaTiO 3 (∼0.2 kJ/mol). A broad frequency dependent dielectric anomaly of unknown origin in the temperature range 250-450 °C was also observed in all samples. © 2012 American Institute of Physics.