Pb Mg1 3 Nb2 3 O3 PbTi O3 superlattices An x-ray diffraction and Raman spectroscopy temperature-dependent study
Résumé
We have used x-ray diffraction and Raman spectroscopy over a broad temperature range (90 K≤T≤900 K) to study the structural and dynamical behavior of [PMN (1-x) Λ (PbTi O3) xΛ] 10 superlattices (x=0.2,0.5,0.8) (where PMN is Pb Mg1 3 Nb2 3 O3), which were epitaxially grown with a nominal wavelength Λ of 130 Å by pulsed laser deposition on MgO substrates buffered with La0.5 Sr0.5 Co O3. We present a comparison of the results obtained on these superlattices with the temperature evolution of three fictitious superlattices constructed using the temperature-dependent data obtained on individual PbTi O3 and Pb Mg1 3 Nb2 3 O3 epitaxial thin films. From this study, we conclude that the PMN layers in superlattices retain the structural characteristics, including the tetragonal distortion, of relaxor thin films. The PbTi O3 layers exhibit in-plane polar orientation at all temperatures. X-ray diffraction shows the stabilization, due to biaxial stress, of the ferroelectric order up to at least 873 K in the PbTi O3 layers (TC =763 K in bulk). The tetragonal symmetry and ferroelectric order of the PbTi O3 layers, as well as the relaxorlike behavior of the PMN layers, are confirmed by Raman spectroscopy. © 2007 The American Physical Society.