Ferroelectric oxides with luminescent ions hold great promise in future optoelectronic devices because of their unique photoluminescence and inherent ferroelectric properties. Intriguingly, the photoluminescence performance of ferroelectric ceramics could be modulated by an external electric field. However, researchers face a current challenge of the diminutive extent and degree of reversibility of the field-driven modification that hinder their use in room-temperature practical applications. Within the scope of current contribution in rare-earth-doped bismuth sodium titanate relaxors, the most important information to be noted is the shifting of the depolarization temperature toward room temperature and the resulting considerable enhancement in ergodicity, as evidenced by the dielectric properties, polarization, and strain hysteresis, as well as the in situ Raman/X-ray diffraction studies. After the introduction of 1 mol % Eu, the induced composition and charge disorders disrupt the original long-range ferroelectric macrodomains into randomly dynamic and weakly correlated polar nanoregions, which facilitates a reversible transformation between polar nanoregions and unstable ferroelectric state under an electric field, engendering a large strain. By virtue of this, both the extent and degree of reversibility of photoluminescence modulation are enhanced (∼60%) considerably, and room-temperature in situ tunable photoluminescence response is then achieved under electric field. These should be helpful for the realization of regulating the physical couplings (photoluminescent-ferroelectrics) in multifunctional inorganic ferroelectrics with a high ergodic state by reversibly tuning the structural symmetry.
Nuclear dynamics in dense hydrogen, which is determined by the key physics of large-angle scattering or many-body collisions between particles, is crucial for the dynamics of planet's evolution and hydrodynamical processes in inertial confinement confusion. Here, using improved ab initio path-integral molecular dynamics simulations, we investigated the nuclear quantum dynamics regarding transport behaviors of dense hydrogen up to the temperatures of 1 eV. With the inclusion of nuclear quantum effects (NQEs), the ionic diffusions are largely higher than the classical treatment by the magnitude from 20% to 146% as the temperature is decreased from 1 eV to 0.3 eV at 10 g/cm3, meanwhile, electrical and thermal conductivities are significantly lowered. In particular, the ionic diffusion is found much larger than that without NQEs even when both the ionic distributions are the same at 1 eV. The significant quantum delocalization of ions introduces remarkably different scattering cross section between protons compared with classical particle treatments, which explains the large difference of transport properties induced by NQEs. The Stokes-Einstein relation, Wiedemann-Franz law, and isotope effects are re-examined, showing different behaviors in nuclear quantum dynamics.
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