Roderic Lakes, Donald Stone (DMR #0520527)
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Microstructure of polycrystalline BaTiO3 by means of reflection optical microscopy in polarized light. Etched 2.5 min. |
Barium Titanate was used as an inclusion in composites that achieve stiffness about ten times as great as diamond. A peak in mechanical damping occurs in barium titanate near the Curie point 125C. The height and width of the peak increase with thermal rate and the inverse of frequency. Bulk modulus softens by about a factor of four during the transition. Recent study shows softening of about a factor of ten. Results are consistent with negative stiffness of small grains under constraint. Poisson’s ratio attains a substantially negative value during the transition. A new phase transition is found near 60 C. Softening of the bulk modulus and negative Poisson’s ratio are observed.
References
L. Dong, et.al, Phys. Stat. Sol. (b) 245, No. 11, 2422–2432 (2008)
