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Effects of Pore Morphology and Grain Size on the Dielectric Properties and Tetragonal–Cubic Phase Transition of High‐Purity Barium Titanate
Author(s) -
Fang TsangTse,
Hsieh HueyLin,
Shiau FuhShan
Publication year - 1993
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.1151-2916.1993.tb03742.x
Subject(s) - dielectric , materials science , barium titanate , curie temperature , tetragonal crystal system , grain size , mineralogy , dissipation factor , porosity , composite material , analytical chemistry (journal) , phase (matter) , condensed matter physics , chemistry , ferromagnetism , physics , optoelectronics , organic chemistry , chromatography
The effects of pore morphology and grain size on the dielectric behavior of high‐purity stoichiometric BaTiO 3 have been intensively investigated. It was found that the dielectric constant was influenced not only by grain size but also by pore morphology. Dielectric constants below the Curie temperature could be evaluated by the Maxwell relationship for specimens with fractional density >90%ρ t and be estimated by the modified Niesel's equation, but depolarization might be involved for specimens with fractional density <90%ρ t . Dielectric Behavior above the Curie temperature followed the Curie–Weiss low. The Curie constants could be separated into two regions depending on the pore morphology, decreasing linearly with increasing porosity at different rates. The results suggest that the tetragonal–cubic phase transition temperature of specimens with fractional density <90%ρ t is affected by depolarization due to the presence of continous channel pores. The dissipation factor was increased with increasing porosity due to the adsorption of water. In this study, a high‐density (<99%ρ t ), uniform, and fine‐grained (∼1.2 μm) microstructure of high‐purity stoichimetric barium titanate has been produced by using wet processing ad pressureless sintering, in which a high dielectric constant (>6100 at 25°C and 1 kHz) and a low dissipation factor (<0.025) could be achieved.