Dielectric relaxation in Li-doped KTaO3studied by kinetic Monte Carlo

Abstract

The dielectric properties of Li-doped KTaO 3 are studied by kinetic Monte Carlo, using a microscopic model derived from first-principles calculations. The method allows equilibrium and nonequilibrium simulations on very large time scales inaccessible by a molecular dynamics simulation and adequately reproduces most of the peculiar characteristics of the system: dielectric relaxation, evolving with increasing Li content of the temperature dependence of the dielectric permittivity (from single to double peaked). The real and imaginary parts of the latter are computed as a function of temperature and frequencies of the external probing electric field (from ≈ 8 kHz to ≈80 MHz) at three Li concentrations (0.9%, 3.0%, and 5.8%). The first-neighbor pairs of Li are evidenced to lead to the double-peaked permittivity as Li concentration increases. Our approach opens a way to an efficient simulation of relaxor ferroelectrics on mesoscopic time scales, while keeping basic ingredients derived from atomic-scale simulations.

Effects of A-Site Ions on the Phase Transition Temperatures and Dielectric Properties of (1-x)(Na0.5K0.5)NbO3–xAZrO3 Solid Solutions

“…Factors that affect the ferroelectric phase transition temperature of perovskite oxides A 0 B 0 O 3 have been extensively studied. [15][16][17][18][19][20][21][22][23][24][25][26] Taking PbTiO 3 and BaTiO 3 as examples, theoretical studies based on the first-principles calculations revealed that the hybridization between the Ti 3d states and O 2p states is essential to generation of the ferroelectric instability in both PbTiO 3 and BaTiO 3 , and that the interaction between the Pb 6s and O 2p states is covalent and crucial for the higher phase transition temperature of PbTiO 3 , 15,16) whereas the interaction between Ba and O is almost ionic for BaTiO 3 . 17) Experimental results showed that the tolerance factor t ¼ ðr…”

“…It has been confirmed that an off-center occupation of dopant ions could induce an effective dipole around it and thus enhance the ferroelectricity of the solid solution. [20][21][22] It is considered that Ca 2þ ions in A = Ca solid solution are located in the off-center position and thus enhanced the ferroelectricity of the solid solutions, leading to a higher T C{T of A = Ca solid solution than that of A = Sr solid solution.…”

Simulating the Radio-Frequency Dielectric Response of Relaxor Ferroelectrics: Combination of Coarse-Grained Hamiltonians and Kinetic Monte Carlo Simulations

“…Our KMC code is similar to the one used in Ref. 20. Once the supercell constructed, the blocks are divided in two categories: (i) polar blocks, (ii) non-polar blocks.…”

Normal and abnormal dielectric relaxation behavior in KTaO3 ceramics

“…16,17 Therefore, much attention has been paid to investigate the dielectric properties of KT induced by alien impurities. [18][19][20][21][22][23][24] However, compared with alien defects, the ubiquitous native point defects-oxygen vacancies (V O s) are widely known to be the "culprit" for various properties of perovskite oxides. 25 In particular, V O s are capable to induce a polarized state in KT due to lattice distortion, as reported in other perovskites.…”