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High‐Permittivity Double Rare‐Earth‐Doped Barium Titanate Ceramics with Diffuse Phase Transition
Author(s) -
Lu DaYong,
Toda Masayuki,
Sugano Mikio
Publication year - 2006
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2006.00893.x
Subject(s) - barium titanate , curie temperature , materials science , analytical chemistry (journal) , dielectric , permittivity , doping , microstructure , ceramic , mineralogy , titanate , vacancy defect , scanning electron microscope , perovskite (structure) , phase transition , orthorhombic crystal system , crystallography , crystal structure , condensed matter physics , chemistry , composite material , optoelectronics , physics , ferromagnetism , chromatography
On the basis of Ti‐vacancy defect compensation mode, high‐permittivity La‐ and Ce‐doped barium titanate ceramics (BLTC) with perovskite structure, i.e., (Ba 1− x La x )(Ti 1− x /4− y Ce y )O 3 , where x =0.01–0.05 and y =0.05, were prepared by conventional ceramic processing techniques. Dielectric characteristics, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and hysteresis loops were measured. Defect chemistry and diffuse phase transition (DPT) in BLTC are discussed. Co‐doping with the relatively smaller La 3+ ions at Ba sites and the relatively larger Ce 4+ ions at Ti sites in the BaTiO 3 host lattice resulted in a fine‐grained microstructure (0.8–1.1 μm), marked raising, and broadening of the Curie peak characteristic of DPT. The Curie temperature ( T C ) at 800 Hz decreased rapidly at a dramatic rate of −30°C/at.% La when y =0.05. By means of co‐doping with La and Ce, this is the first time that high k “Y5V” ceramics (BLTC: 0.03≤ x ≤0.04, y =0.05) with ɛ′ RT >10 000 over a frequency range of 1–100 kHz have been achieved in rare‐earth‐doped BaTiO 3 ceramics.