Portal de Periódicos da CAPES

Effect of the phase transition of on the ion conduction in - Teflon composites

1997; IOP Publishing; Volume: 9; Issue: 20 Linguagem: Inglês

10.1088/0953-8984/9/20/011

1361-648X

Ana Martı́nez-Juárez, Ricardo Jiménez, P. Durán-Martı́n, Joaquı́n Ibáñez, J. M. Rojo,

Material Dynamics and Properties

A composite - 25% vol Teflon was prepared to prevent breakages in powder pellets due to the phase transition of and, thus, to study the effect of the phase transition on conduction. The composite microstructure, as followed by scanning electron microscopy, shows aggregated particles surrounded by Teflon regions which operate as a skeleton. The imaginary part of the electric modulus shows two peaks at high and low frequency which are ascribed to grain-interior and grain-boundary response, respectively. In the two phases the ionic conductivity inside the grains is about three orders of magnitude larger than that found for the grain boundary. The phase transition affects the activation energy in different ways. It decreases for the grain-interior response from 0.68 eV for the low-temperature phase to 0.34 eV for the high-temperature phase, while it increases from 0.45 to 0.56 eV for the movement through the grain boundaries. An anomalous increase in activation energy for the grain-interior response in the high-temperature phase before it is transformed into the low-temperature phase has been found.