posted on 2022-11-14, 13:35authored byMégane Lheureux, Marie-Hélène Chambrier, Kevin Dalla Francesca, Beatriz Vargas, Lluis Yedra, Antonio Da Costa, Thomas Carlier, Florent Blanchard, Sonia Estradé, Francesca Peiro, Pascal Roussel, Jean-François Blach, Anthony Ferri, Rachel Desfeux
An orthorhombic α-Pr2WO6 (PrWO)
polymorph
with a = 16.57(5) Å, b = 5.52(5)
Å, and c = 8.73(1) Å, isostructural to
α-La2WO6 and α-Nd2WO6, has been stabilized in the form of thin film by pulsed laser
deposition on (001)-oriented SrTiO3 substrates. Combining
X-ray diffraction pole-figure measurements and transmission electron
microscopy (TEM) analysis, the c-axis films gave
evidence of the orientations [100]PrWO || [110]STO and [010]PrWO || [110]STO in the plane. Advanced φ-scans and reciprocal space mapping
characterizations confirm the existence of the orthorhombic (Pm21n) structure in the film
in place to the tetragonal one as also suggested. X-ray thermodiffraction
measurements highlight the stability of this polymorph in thin film
up to 900 °C at least. Optical measurements performed by spectroscopic
ellipsometry reveal that the band gap in such 36 nm thick films (as
confirmed by both X-ray reflectivity and TEM measurements) is 2.5
eV. Besides, the local piezoelectric hysteresis loops recorded by
using the spectroscopic tool of piezoresponse force microscopy attest
to the robustness of the piezoelectricity and ferroelectricity in
these α-Pr2WO6 films. This study demonstrates
the existence of a new lead-free ferroelectric material in the series
of α-Ln2WO6 (lanthanide) tungstates, which
can be considered as a promising candidate for applications in both
nanoelectromechanical and energy-harvesting systems as well as for
integrating optics.