Dielectric model of point charge defects in insulating paraelectric perovskites

Artikel i vetenskaplig tidskrift, 2011

Some point defects (i.e., oxygen vacancies) create deep trapping levels in the bandgap of the paraelectric phase ferroelectric crystals. Under applied DC field the traps release electrons via the Poole-Frenkel mechanism and become charged. The electric field of a point charge polarizes the crystal locally reducing its permittivity. In this paper a simple theory is proposed for calculating the DC field dependent apparent (measureable) permittivity of a paraelectric crystal with point charge defects. It is shown that the apparent permittivity of a paraelectric crystal may be sufficiently lower as compared with the defectless crystal. This reduction is in addition to the possible reduction of the apparent permittivity associated with the interfacial "dead" layers and strain.