Synthesis, Structure, and Properties of Bi_(3.25)Pr_(0.75)Ti_(2.97)V_(0.03)O_(12) Ferroelectric Ceramics

摘要

Praseodymium and vanadium cosubstituted Bi_4Ti_3O_(12) was synthesized using a modified citrate-gel method. The crystallization was promoted by the oxidation of residual carbon produced by decomposition of - CH_x groups resulting in a crystallization temperature as low as 450 °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 °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 Pr~(3+) and V~(5+) cosubstituted Bi_4Ti_3O_(12) 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.