Stress and electric field gradient contributions to dielectric loss in ferroelectrics with interdigitated electrodes

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Interdigitated electrode configurations produce nonuniform electric field and stress in the vicinity of the electrodes, creating a volume where the material is not uniformly polarized. This results in enhanced hysteresis in interdigitated electrode configurations relative to the hysteresis in the bulk material. The dielectric loss in a macro-fiber composite with interdigitated electrodes was characterized and is compared to the dielectric loss of the same material under a uniform field. The dielectric loss in the interdigitated electrode arrangement was found to be significantly larger and had a strong dependence on electric field amplitude. The dielectric loss is expressed in terms of an effective loss tangent (tan δ) and a more general damping model. A mechanism that contributes to the hysteresis is that the local stress in the ferroelectric material beneath the interdigitated electrodes induces ferroelastic polarization reorientation during each electric field cycle. The interactions between polarization gradients and residual stress are assessed using a finite element model with a micromechanical-based constitutive law.