A first-principles-based model is developed to investigate the influence of lead vacancies on the properties of the disordered $\mathrm{Pb}\left({\mathrm{Sc}}_{1∕2}{\mathrm{Nb}}_{1∕2}\right){\mathrm{O}}_3$ (PSN) ferroelectric. Lead vacancies generate large, inhomogeneous, electric fields that reduce barriers between energy minima for different polarization directions. This naturally explains why disordered ferroelectrics with significant lead vacancy concentrations have broadened dielectric peaks at lower temperatures, and why lead vacancies smear properties in the neighborhood of the ferroelectric transition in PSN. We also reconsider the conventional wisdom that lead vacancies reduce the magnitude of dielectric response.

• Received 8 September 2006

DOI:https://doi.org/10.1103/PhysRevB.75.014111