Synthesis, structure, and properties of Bi3.25Pr0.75Ti2.97V0.03O12 ferroelectric ceramics

Praseodymium and vanadium cosubstituted Bi4Ti3O12 was synthesized using a modified citrate-gel method. The crystallization was promoted by the oxidation of residual carbon produced by decomposition of -CHx groups resulting in a crystallization temperature as low as 450 degrees C. The as-synthesized powder consisted of uniform spherical particles with a mean size of 57 nm and a standard deviation of 14 nm. The ceramic prepared from the as-synthesized powder at 900 degrees C consisted mainly of randomly arranged platelets with a thickness of 200 nm. The Rietveld refinement in the orthorhombic space group Aba2 for the as-prepared Pr3+ and V5+ cosubstituted Bi4Ti3O12 resulted in a convergent refinement (R-wp = 5.01%). The remanent polarization (2P(r)) and coercive field (2E(c)) values measured at room temperature with a maximum electric field of +/- 300 kV/cm were 35 mu C/cm(2) and 148 kV/cm, respectively. The ceramic has a very low ohmic conductivity, and the leakage current density is below 1 mu A/cm(2) up to 200 kV/cm. No profound fatigue was observed after switching over 10(8) cycles. The evolution of 2E(c), 2P(r), P-max (maximum polarization), and P-max/P-r with E-max (maximum electric field) is discussed using an ideal and a four components ferroelectric capacitor model. The observed linear relationship between P-max/P-r and E-max provides the possibility to calculate the field independent dielectric constant (282) and nonremanent polarization (2.7 mu C/cm(2) at E-max = 300 kV/cm) for the ceramic studied.