Js. Capurso et al., PROCESSING OF LAMINATED BARIUM-TITANATE STRUCTURES FOR STRESS-SENSINGAPPLICATIONS, Journal of the American Ceramic Society, 78(9), 1995, pp. 2476-2480
High-purity, chemically prepared barium titanate was doped with 0.3 at
.% lanthanum and, in some cases, counter-doped with 0.04 at.% manganes
e by precipitation. Using standard techniques, tape-cast sheets of the
positive temperature coefficient of resistance (PTCR) compositions as
well as the base insulating powder were made. A multilayer sensor was
laminated and sintered, with upper and lower PTCR regions separated b
y an insulating BaTiO3, region. The sensor was loaded using a four-poi
nt bend test configuration. The change in resistivity with increased l
oad was observed to be linear, with positive and negative piezoresisti
ve coefficients for the PTCR layers under compression and tension, res
pectively. These trends were in general agreement with a stress-depend
ent permittivity and the Heywang model of grain-boundary potential bar
riers. Piezoresistivity values were derived from the resistivity-stres
s slope; these were examined as a function of temperature and sensor g
eometry.