Average and local atomic-scale structure in BaZrxTi(1-x)O3 (x = 0. 10, 0.20, 0.40) ceramics by high-energy x-ray diffraction and Raman spectroscopy.
High-resolution x-ray diffraction (XRD), Raman spectroscopy and total scattering XRD coupled to atomic pair distribution function (PDF) analysis studies of the atomic-scale structure of archetypal BaZrxTi(1-x)O3 (x = 0.10, 0.20, 0.40) ceramics are presented over a wide temperature range (100-450 K). For x = 0.1 and 0.2 the results reveal, well above the Curie temperature, the presence of Ti-rich polar clusters which are precursors of a long-range ferroelectric order observed below TC. Polar nanoregions (PNRs) and relaxor behaviour are observed over the whole temperature range for x = 0.4. Irrespective of ceramic composition, the polar clusters are due to locally correlated off-centre displacement of Zr/Ti cations compatible with local rhombohedral symmetry. Formation of Zr-rich clusters is indicated by Raman spectroscopy for all compositions. Considering the isovalent substitution of Ti with Zr in BaZrxTi1-xO3, the mechanism of formation and growth of the PNRs is not due to charge ordering and random fields, but rather to a reduction of the local strain promoted by the large difference in ion size between Zr(4+) and Ti(4+). As a result, non-polar or weakly polar Zr-rich clusters and polar Ti-rich clusters are randomly distributed in a paraelectric lattice and the long-range ferroelectric order is disrupted with increasing Zr concentration.
Institute for Energetics and Interphases, National Research Council (IENI-CNR), Via De Marini 6, I-16149 Genova, Italy.
Vincenzo
V
Buscaglia
Saurabh
S
Tripathi
Valeri
V
Petkov
Monica
M
Dapiaggi
Marco
M
Deluca
Andreja
A
Gajović
Yang
Y
Ren
D002516:Ceramics / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction; D015040:Zirconium / Q000737:chemistry*
D010087:Oxides; D015040:Zirconium; D014025:Titanium