Dielectric Mixing as Evidenced in a Wide Range of (Sr_0.8Pb_0.2)TiO₃-MgO Composites

Using a composite of a high dielectric permittivity (ϵ) ferroelectric and low ϵ oxide to check dielectric mixing rules, often the high ϵ ferroelectric is strongly sensitive to elastic and dielectric boundary conditions. So its ϵ changes as volume fraction and microstructure change invalidating any checking. In the strontium lead titanate (SPT)-magnesium oxide composites reported here, the SPT is well above its Curie point and much less sensitive, however, both phases contain pores. Since the pore fractions are low and almost constant, the system may be treated as quasi-two-phase and is found to follow closely the model proposed by Wakino.

Keywords:

• Composite
• mixing rule
• dielectric constant
• strontium lead titanate

Acknowledgments

Financial support was partially provided by the DARPA under contract No. DABT 63-98-1-002.