Ferroelectric Q-phase in a NaNbO 3 epitaxial thin film

Epitaxial NaNbO 3 thin films have been grown by pulsed laser deposition on cubic (00l) MgO substrate with epitaxial ( La 0.5 Sr 0.5 ) CoO 3 buffer layer. Micro-Raman spectroscopy studies revealed that the ferroelectric Q phase ( P m c 2 1 , Z = 4 ) is stable in a 250-nm-thick film in contrast to the antiferroelectric phase P ( P b m a , Z = 8 ) known to exist in the bulk single crystals and ceramics of undoped stoichiometric NaNbO 3 . Temperature-dependent Raman spectra indicate that the Q phase is stable over a wide temperature range (at least from 80 to 600 K), while the low-temperature ferroelectric rhombohedral phase N, typical for NaNbO 3 single crystals, is not observed.