Nanocomposites for Electronic Applications
Final rept. 1 Oct 1988-30 Sep 1989
PENNSYLVANIA STATE UNIV STATE COLLEGE
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This document reports work carried out over the third year of a University Research Initiative URI on Nanocomposites for Electronic Application. Over the year the work has moved more towards the detailed study of the relaxor ferroelectrics as a model system for self assembling nanocomposites. In the perovskite structure lead magnesium niobate PMN a sequence of studies of the kinetics of the polarization process under both weak and high electric fields points up the close similarity of PMN to the magnetic spin glass systems. Application of the Vogel-Fulcher relation predicts the kinetics of the freezing process which immobilizes the micro-polar structure, and permits calculation of the relaxation at higher temperatures and frequencies. Studies of internal friction relate this behaviour to the dielectric through conventional electrostriction. New evidence has also been obtained through TEM observations of the order-disorder of B site cations in the AB1B2O3 structure which gives rise to the fossil chemistry and nano-polar response. In the tungsten bronze structure relaxors a major breakthrough is the clear documentation of spin glass behaviour in an already polar matrix, for properties in directions orthogonal to the polar axis. For the BaxPb1-x-Nb2O6 solid solutions at compositions close to the morphotropic phase boundary MPB this behaviour is seen in both ferroelectric tetragonal and orthorhombic species.
- Inorganic Chemistry