Design of superior electrostriction in BaTiO_(3) -based lead-free relaxors via the formation of polarization nanoclusters

Electrostrictive materials have wide applications in modern high-precision electronic devices.Driven by growing environmental concerns,there is demand for lead-free materials with superior electrostriction behaviors.In this study,we demonstrate a record-high electrostrictive coefficient of~0.0712 m^(4) C^(-2) in perovskite ferroelectric ceramics,along with hysteresis-free strain as well as excellent frequency and thermal stabilities,in lead-free BaTiO_(3)-based ceramics through a polarization nanocluster design.By appro-priately introducing Li+and Bi^(3+)into the BaTiO 3 lattice matrix,the long-range ferroelectric ordering can be broken,and polarization nanoclusters can be formed,resulting in a relaxor state with concurrently suppressed polariza-tion and maintained electro-strain.A three-dimensional atomic model constructed using advanced neutron total-scattering data combined with the reverse Monte Carlo method indicates the existence of Bi and Li segregations at the subnanometer scale,which confirms the prediction made by density functional theory calculations.Such a short-range chemical order destroys the long-range ferroelectric order of the off-centered Ti polar displacements and leads to the embedding of Li+/Bi ^(3+)-rich polar nanoregions in the Ba^(2+)-rich polarization disorder matrix.Further,a completely reversible electric-field-induced lattice strain is observed,giving rise to pure electrostriction without hysteresis behavior.This work provides a novel strategy for developing lead-free relaxor ferroelectrics with high electrostriction performance.

Constructive strategies for drug delivery systems in antivirus disease therapy by biosafety materials

Due to the coronavirus disease 2019(COVID‐19)pandemic,the development of antiviral drugs has attracted increasing attention.Clinical antiviral drugs show weak solubility,low bioavailability,adverse side effects,or only limited targets.With the advancement of nanotechnology and material science,biosafety nanomaterials have been constructed for drug delivery systems of antiviral disease therapy,such as liposomes,polymers,gold nanoparticles,and graphene.These nanodrug systems can either deliver synthesized antiviral drugs siRNA/miRNA and small molecular compounds,deliver bioactive large molecular drug proteins and mRNA,or show antiviral activity by themselves.Nanodelivery systems could effectively enhance the efficiency of antiviral drugs by increasing drug loading and host cell uptake with a small size and high specific surface area.This review focused on the biosafety nanomaterials used for antiviral therapy and discussed the options for the design of antiviral drugs in the future.