Multiferroic And Microwave Absorption In （1-x）BiFeO₃-x（BiNa）_0.5TiO₃Solid Solution

Single phase multiferroic materials with coexistence of more than one ferroic whichcoupled with each other, display not only the characteristics of both the traditionalferroelectric（FE） and ferromagnetic（FM） materials, but also the the magnetoelectriccoupling feature which provide a completely new degree of freedom for design of newdevices, making them very appealing in potential applications. The unique physicalcontent of single phase multiferroic materials is also very meaningful for the developmentof the theory of condensed matter physics. So far, researchers have found more than onehundred single-phase multiferroic materials, and conducted extensive exploration of thesemultiferroic coexistence mechanism. Unfortunately, few of these single phase multiferroicmaterials can exhibit the coexistence of FE and FM above room temperature. BiFeO₃,asone of those room temperature single phase multiferroic materials, its potential applicationpossibilities attracted wide attention from researchers. However, there are some fatalproblems, Huge leakage current, generation miscellaneous phase in synthesis process,special magnetic structure destroying macroscopic magnetic and so on, preventing theapplications of BiFeO₃. Experiments confirmed that solid solution formed with BiFeO₃and another FE perovskite material can efficiently improve multiferroic of BiFeO₃.BiFeO₃with coexistense of FM and FE properties, can cause magnetic loss and electricalloss in microwave field simultaneously. Improvement of multiferroic of BiFeO₃by solidsolution maybe produce a candidate for microwave absorbing material.This paper attempts to synthesis （1-x）BiFeO₃-x（BiNa）_0.5TiO₃solid solution, a newtype of multiferroic ceramic material, and explore the microwave absorption properties ofthe solid solution. The main content of the paper is as follows:1) Citric acid-Nitrate method was used to synthesis （1-x）BiFeO₃-x（BiNa）_0.5TiO₃（x=0 0.6） solid solution. These solid solution characterized with XRD and SEM, showstructural phase transition with increase of （BiNa）_0.5TiO₃in the solid solution. Thisstructural phase transition is the fundamental cause of the room temperatureferroelectric and ferromagnetic in the solid solution. Intensity and coexistence offerroelectric and ferromagnetic properties can be achieved through solid solubility.We argues that morphotropic phase boundary is one of the key influencing factors forchanges of the solid solution ferroelectricity; the magnetic changes can attribute to thedestruction of the spiral magnetic structure and the Fe-O-Ti-O-Fe long-rangesuperexchange interactions.2) Some of the solid solution （x=0.1to0.4） with good ferroelectric and magneticproperties, were chosen for microwave absorption test with a vector network analyzer,measuring the complex permeability and permittivity within the frequency range of2-18GHz. The reflection losses was calculated according to the coaxial theoreticalmethod. Complex permittivity and permeability of solid solution shows mainlynatural resonance loss. Complex permeability is smaller than the complex permittivity,which leads to the impedance mismatch and the microwave absorbing properties isnot satisfactory.