Discrimination of polar order extent in BaZrxTi1-xO3 epitaxial thin films by Raman spectroscopy

Raman spectroscopy studies of BaZrxTi1-xO3 (BZT) epitaxial thin films are presented over the entire compositional range (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1). The analysis of the results has allowed the elaboration of the phase diagram of the BZT thin films in which three types of ferroelectric behaviour were distinguished based on the polar order extent: long range conventional ferroelectricity for x ≤ 0.2, relaxor behaviour for 0.3 ≤ x ≤ 0.7 and weak polar interaction for 0.8 ≤ x ≤ 0.9. In order to verify the validity of this phase diagram, Raman spectra of the films were also performed over a wide temperature range (from 97 K to 497 K). The results reveal that the presence or absence of a temperature dependent structural transition correlates with the polar order extent and, thus, the ferroelectric behaviour of BZT.