A nanodomain morphology comprising fine structures of less than 5 nm spacing was observed in oxygen deficient lead zirconate titanates modified by La, Ca, and Sr. Oxidation of samples can eliminate the fine structures and facilitate polarization switching. Although grain growth after high temperature annealing results in normal domain morphology and complete polarization switching, irregular and fragmented domains remain. These fine domain structures were explained in terms of local polarization pinning due to oxygen vacancies and antisite substitutents.