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Microscopic Origin of the PTC Effect in Niobium‐Doped Barium Titanate
Author(s) -
Gillot Cristophe,
Michenaud JeanPierre,
Baukens Isabelle,
Duvigneaud PaulHenri
Publication year - 1997
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.1151-2916.1997.tb02944.x
Subject(s) - barium titanate , materials science , curie temperature , grain boundary , niobium , doping , electrical resistivity and conductivity , condensed matter physics , phase boundary , conductivity , barium , phase (matter) , mineralogy , microstructure , composite material , optoelectronics , metallurgy , chemistry , ceramic , physics , organic chemistry , quantum mechanics , ferromagnetism
The influence of bulk conductivity on the PTC effect of Nb‐doped barium titanate is investigated. Both macroscopic and microscopic resistance measurements are performed as a function of temperature. The macroscopic measurement refers to the whole sample while the microscopic one, obtained by photolithography techniques, concerns only several grains. The results show that the increase of resistivity occurs in two steps: first, an abrupt variation at the Curie temperature T c which is ascribed to the phase transition in the bulk; second, a continuous increase above T c which is usually explained from grain boundary potential barriers only. However, our results suggest that a nonnegligible contribution of the bulk is also involved in this increase above T c .