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Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties
Published on: August 15, 2015
Incipient Modulated Phase in Sr_{1-x}Ca_{x}TiO_{3}
Benoît Fauqué1, Daniel A Chaney2, Philippe Bourges3
1Université PSL, ESPCI Paris, CNRS, Laboratoire de Physique et d'Etude de Matériaux, (, ) , 75005 Paris, France.
None:
Nanometer-scale modulations can spontaneously emerge in complex materials when multiple degrees of freedom interact. Here we demonstrate that ferroelectric Sr_{1-x}Ca_{x}TiO_{3} lies in close proximity to a finite-q lattice instability associated with a tendency toward structural modulation. Using inelastic neutron and x-ray scattering, we show that upon cooling, dipolar fluctuations strongly couple to and soften the c_{44} transverse acoustic mode. We identify the wave vector at which this softening is maximal, thereby defining the characteristic length scale of the instability. Calcium substitution enhances both the amplitude and the wavevector of the softening by strengthening the ferroelectric and antiferrodistortive instabilities. Our results demonstrate that the flexoelectric phonon coupling promotes a tendency toward a dynamically modulated state that cooperates with, rather than competes against, the other lattice instabilities in SrTiO_{3}.
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