Role of the soft dielectric energy in poling ceramics, glass-like systems and in domain average engineering

Abstract

In the classical approach of interpreting the process of poling ceramics, the energy F/sub 1/=-E/sub i/P/sub Si/ is considered to be the decisive source of the procedure. However, induced polarization of anisotropic grains also contributes to the free energy. The corresponding term F/sub 2/=-( 1/2 )/spl epsi//sub ij/E/sub i/E/sub j/ may influence the poling process. Its possible role is discussed using a 2D model and taking into account the dielectric anisotropy and its temperature dependences. It is shown that for low applied fields (E E*) the energy F/sub 2/ plays the decisive role and the P/sub s/ vector needs not to acquire the orientation closest to the field E. In the intermediate region of fields the influences of both energy contributions compete. In a similar way, the piezoelectric energy -d/sub ij/E/sub 1/T/sub jk/ can be involved in the process, where the stress T/sub jk/ is applied and influenced by mutual clamping of grains or particles in glassy systems. The energy of a soft dielectric can also influence the results when devising domain-average-engineered samples of single-crystalline ferroics: crystalline specimens divided into a very large number of domains, representing /spl mu/ domain states where /spl mu/ is smaller than the theoretically allowed maximum number.