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Electrical Properties of Boron Nitride Matrix Composites: III, Observations near the Percolation Threshold in BN–B 4 C Composites
Author(s) -
Gerhardt Rosario A.,
Runyan Julie,
Sana Catherine,
McLachlan David S.,
Ruh Robert
Publication year - 2001
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.1151-2916.2001.tb01011.x
Subject(s) - percolation threshold , electrical resistivity and conductivity , materials science , composite material , percolation (cognitive psychology) , boron nitride , composite number , degree (music) , boron , chemistry , physics , neuroscience , acoustics , biology , organic chemistry , quantum mechanics
In this third paper of the series, we discuss the electrical resistivity of BN–B 4 C composites with compositions ranging from 0% to 100% B 4 C. After establishing the response of samples whose compositions lie far away from the percolation region, where effective medium models apply, we focus attention on samples with compositions at or near the percolation threshold (∼60% BN–40% B 4 C). The large differences in electrical properties among samples with the same nominal composition can be explained by invoking a connectivity parameter. Since the difference in the electrical resistivity of BN and B 4 C is about 9 orders of magnitude, the degree of connectivity of the two components at the percolation threshold determines the resultant composite resistivity. Connectivity in these composites was quantified by taking BN peak height ratios in X‐ray diffraction patterns of all samples containing 60% BN–40% B 4 C. The degree of preferred orientation of the BN platelets can be correlated with systematic increases in the electrical resistivity of the composites.