Quantum-fluctuation-stabilized orthorhombic ferroelectric ground state in lead-free piezoelectric (Ba,Ca)(Zr,Ti )O3

Alireza Akbarzadeh (1) , Brajesh Kumar (2) , Yousra Nahas (1) , Naveen Kumar (2) , Sergei Prokhorenko (1) , Diptikanta Swain (3) , Sergey Prosandeev (1) , Raymond Walter (1) , Igor A. Kornev (4) , Jorgé Iñiguez (5) , Brahim Dkhil (4) , Rajeev Ranjan (2) , L. Bellaiche (1)

1 Department of Physics Department [Fayetteville]
2 Department of Mathematics (Bangalore)
3 Solid State and Structural Chemistry Unit
4 SPMS - Laboratoire Structures, Propriétés et Modélisation des solides
5 LIST - Luxembourg Institute of Science and Technology

We numerically investigate the phase diagram of the giant-piezoelectric (1−x)Ba(Zr0.2Ti0.8)O3−x(Ba0.7Ca0.3)TiO3 system, treating the ions either as classical objects (via classical Monte Carlo or CMC simulations) or quantum mechanically (via path-integral quantum Monte Carlo or PI-QMC simulations). It is found that PI-QMC not only provides a better agreement with available experimental data for the temperature-composition phase diagram, but also leads to the existence of an orthorhombic ground state in a narrow range of composition, unlike CMC that “only” yields ground states of rhombohedral or tetragonal symmetry. X-ray powder diffraction experiments are further conducted at 20 K. They confirm the occurrence of a quantum-fluctuation-induced orthorhombic state for some compositions and therefore validate the PI-QMC prediction. The role of quantum effects on the local structure, such as the annihilation of a homogeneous rhombohedral system in favor of an inhomogeneous mixing of orthorhombic and rhombohedral clusters, is also documented and discussed.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Alireza Akbarzadeh, Brajesh Kumar, Yousra Nahas, Naveen Kumar, Sergei Prokhorenko, et al.. Quantum-fluctuation-stabilized orthorhombic ferroelectric ground state in lead-free piezoelectric (Ba,Ca)(Zr,Ti )O3. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2018, 98 (10), pp.104101. ⟨10.1103/PhysRevB.98.104101⟩. ⟨hal-01885613⟩