MICROSCOPIC ORIGIN OF THE PTC EFFECT IN NIOBIUM-DOPED BARIUM-TITANATE

Citation
C. Gillot et al., MICROSCOPIC ORIGIN OF THE PTC EFFECT IN NIOBIUM-DOPED BARIUM-TITANATE, Journal of the American Ceramic Society, 80(4), 1997, pp. 1043-1046
Citations number
20
Categorie Soggetti
Material Science, Ceramics
ISSN journal
00027820
Volume
80
Issue
4
Year of publication
1997
Pages
1043 - 1046
Database
ISI
SICI code
0002-7820(1997)80:4<1043:MOOTPE>2.0.ZU;2-5
Abstract
The influence of bulk conductivity on the PTC effect of Nb-doped bariu m titanate is investigated. Both macroscopic and microscopic resistanc e measurements are performed as a function of temperature. The macrosc opic 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 step s: first, an abrupt variation at the Curie temperature T-c which is as cribed to the phase transition in the bulk; second, a continuous incre ase above T-c which is usually explained from grain boundary potential barriers only. However, our results suggest that a nonnegligible cont ribution of the bulk is also involved in this increase above T-c.