Crystal structure, dielectric, ferroelectric and energy storage properties of La-doped BaTiO_3 semiconducting ceramics

摘要

Polycrystalline La-doped BaTiO_3 (Ba_(1-x)La_xTiO_3) [x = 0,0.0005,0.001,0.003] ceramics (denoted as BTO,BLT1,BLT2,BLT3) were synthesized by conventional solid-state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. XRD and Raman spectra revealed single-phase tetragonal perovskite crystalline structure. Well-saturated polarization-electric field (P-E) hysteresis loops were observed with the measurement frequency of 50 Hz at room temperature and confirmed ferroelectric nature of these ceramics and a high recoverable electrical energy storage density of 0.350 J/cm~3 with energy efficiency (n) ～ 9%, which is useful in energy storage capacitor applications. Dielectric studies revealed anomalies around 415-420 K and near the Curie temperature. The latter is attributed to the ferroelectric to paraelectric phase transition. Better dielectric performances were obtained for La-doped samples sintered at 1350℃ for 4 h. Grain growth is inhibited with lanthanum (La) incorporation into the BTO lattice. Room temperature semiconducting behavior with positive temperature coefficient of resistivity (PTCR) behavior at T_C is attributed to electron compensation mechanism.