Free energy variation due to a space charge formation

Abstract

A polycrystalline ceramic (Y/sub 2/ O/sub 3/ + 1 at.% La) has been charged under electron irradiation. The specific heat C/sub p/ of both an uncharged and of a charged sample has been measured by the microcalorimetric technique, showing that C/sub p/ decreases after charge implantation. The variation of C/sub p/(T) as a function of the temperature of the charged sample has also been investigated. The extra contribution of the polarization introduced in C/sub p/ vanishes at about 400/spl deg/C. The variation of C/sub p/ after charging and the observed dipolar relaxation in Y/sub 2/O/sub 3/ are interpreted with a simple qualitative model. It has been shown that charge trapping modifies the thermodynamic variables of insulators and therefore can be at the origin of structural modifications in a variety of materials subject to stresses such as the recrystallization of polymers or the phase transition of zirconia.<>