Induced displacive transition in heterogeneous materials

¹ Department of Theoretical Physics, Institute of Atomic Physics, Magurele-Bucharest MG-6, PO Box MG-35, Romania
² MIRA Technologies Ltd., Teiul Doamnei 2, Bucharest, Romania
³ MIRA Telecom, Grigorescu 13, 075100 Otopeni, Bucharest, Romania

^a e-mail: apoma@theory.nipne.ro

Received: 8 May 2012
Revised: 31 May 2012
Accepted: 31 May 2012
Published online: 11 July 2012

Abstract

A model of heterogeneous, composite material is introduced, consisting of randomly distributed identical structural micro-domains endowed with electric charges or dipoles. Two cases are presented, one corresponding to a tightly packed (dense) material, another corresponding to highly-dispersed, small domains. The polarizability is computed in both cases, under the action of an external uniform electric field oscillating in time (a quasi-stationary field), and it is related to the displacement of the micro-domains from their positions of local equilibrium (translations or rotations). It is shown that the polarizability (or electric susceptibility) can exhibit characteristic (resonance) frequencies in the radio-frequency range and, even for moderate external fields, the material can undergo a displacive transition (similar to a ferroelectric transition), governed by non-linearities in the interaction energy of the micro-domains. The shift in the characteristic frequencies of the polarizability is estimated, as caused by the displacive modification.