Effect Of Superlattice-like Structure On The Properties Of Intergrowth Layered Oxides

The quantum functional compound oxide is a material of which native parameters?including charges,orbits,and spin degrees of freedom?can function with external fields?such as optical,electrical,magnetic,acoustic,and thermal field?.The response of quantum functional materials to various external fields and the coupling between its native parameters provide a very promising application prospect in information transmission,storage,regulation,amplification and development of solid-state quantum devices.Quantum functional oxides have become an important topic for current material research and study.However,despite the efforts of several generations of people who have achieved more mature materials systems and research results,the complex regulation and coupling of various parameters is still not very satisfactory,and the corresponding theoretical basis is still not perfect.Therefore,further study on the quantum functional oxides to design and explore new materials and to promote the related theory development have both theoretical and practical significance in realizing multi-parameter couplings in quantum functional oxides.The layered perovskite-like oxides,because of their special structures,can achieve couplings of ferroelectric,ferromagnetic and other parameters on a single axis,attracting more and more attention.Among them,intergrowth structural oxides have exerted a favorable influence on various properties.Most of the current researches have focused on the development of new materials with enhanced performance,while less on the reasons for their structural modulation and performance enhancements.In this paper,two new intergrowth Aurivillius oxides,Bi₃LaTiNbFeO₁₂-BisTi₃FeO₁₅ and Bi₃TiNbO₉-Bi₃LaTiNbFeO₁₂,were synthesized.Their lattice structures and multiferroic properties were studied,and effect of the intergrowth structure on native properties were discussed.These studies may contribute to intensive developing of quantum functional oxides with large electromagnetic coupling.X-ray diffraction investigations and high angle annular dark field scanning projection electron microscopy?HAADF-STEM?results suggested that Bi₃LaTiNbFeO₁₂-Bi₅Ti₃FeO₁₅ and Bi₃TiNbO₉-Bi₃LaTiNbFeO₁₂ have 2-3 and 3-4 layered intergrowth structure.Moreover,XRD refinement and Raman spectra results proved that lattice parameters?a and b?of parent oxides differs a lot between each other,and therefore,may result in a larger internal stress and lattice distortion in the formed compounds with intergrowth structure,similar to those in superlattice.At the same time,ferroelectric,dielectric,and magnetic properties of the new compounds were characterized.It was found that the super lattice-like structure largely contributed to ferroelectric properties?2Pr?and coercive field?2Ec?because of its strong internal stress and large lattice distortion.Meanwhile,the intergrowth structural samples had a lower ferroelectric Curie temperature.Nevertheless,the magnetic measurement results suggested that such intergrowth structure had little effect on the magnetic susceptibility,and magnetization polarizations of samples were mainly affected by the content of magnetic element Fe which was basically in a low spin state in these materials.