| With the rapid development of computer and radio communicationtechnology, electronic devices that can meet the requirements ofminiaturization, multifunction, integration and intelligentization aredemanded. Therefore, electronic materials with excellent properties andmultifuctional properties have recently attracted a great deal ofattention. The multiferroic materials, which are the class of materialsexhibiting coexistence of magnetic and ferroelectric orderings, have theability to couple the electric and magnetic polarizations, providing anadditional degree of freedom in device design. However, there are veryfew natural magnetoelectric single-phase compounds which aresimultaneously ferromagnetic and ferroelectric at room temperature.The Magnetoelectric composites are always attracting the attention ofresearchers. Y3Fe5O12(YIG) is a classical soft ferrite with a highresistivity and low dielectric loss tangent (tanδ) in microwave region.YFeO3(YIP) is a G-type antiferromagnet with a high Néel temperature(TN=645K) and a high resistivity and shows weak magnetic at roomtemperature. Hence, It is commonly used, as magnetic phase, forpreparing magnetoelectric composites.Yttrium ferrite-based magnetoelectric composites were synthesizedvia the solid-state method. The phase composition and surfacemorphology of the composites were investigated using XRD and SEM,respectively. The dielectric and magnetic properties of the compositeswere also studied. Meanwhile, preparation technology and formationmechanism were also studied.(1) Ba0.8Sr0.2TiO3/YFeO3(BST/YIP)composites were synthesizedvia the in-situ growth solid-state method and sintered at1350℃, usingBa0.8Sr0.2TiO3(BST) and Y3Fe5O12as raw materials. The results show that there are BST phase, YIP phase and a small amount of unknownphase in all composites. It can be due to some Ti4+cations diffused fromBST into YIG and made YIG transform to YIP. And the BST/YIPcomposites have giant dielectric constants and high the coercive field.(2) Homogeneous microstructures with few pores were observed inthe BST/YIG/YIP composites. There are BST phase, YIP phase and asmall amount of unknown phase in all composites. The phasetransformation did not decrease the properties of composites. And theBST/YIG/YIP composites have giant dielectric constants and highsaturation magnetization. And for the25%BST/75%(yttrium ferrite)composite, the dielectric constant is about12,000possess large ε’,which is attributed to the interfacial polarization at the interfaces of thetwo components. Meanwhile, the composites posses high saturationmagnetization and the initial permeability.(3)0.71BiFe0.97(Mg0.5Ti0.5)0.03O3-0.29BaTiO3/BiY2Fe5O12(BFO-BT/BYIG) composites were synthesized via the conventional solid-statemethod,0.6wt%MnO2as additive and sintered at1070℃. The resultsshow that BFO-BT phase and BYIG phase can exist individually anddisplay very good chemical compatibility. Meanwile, the compositespresent typical ferroelectricity and ferromagnetism with giant dielectricconstant, high saturation magnetization, low dielectric loss and leakagecurrent. And the value of ε’ and tanδ decrease with increasing of thefrequency. The composites also possess high permeability and lowcoercive field (Hm). For the80%(BFO-BT)/20%BYIG composite, thesaturation magnetization and coercive field are about5emu/g and100Oe, respectively.(4) The BaTiO3/BiY2Fe5O12(BT/BYIG) composites were usednano-sized BaTiO3, BiY2Fe5O12as raw materials, Li2CO3assintering-aid and sintered at1100℃. The results show that BT phaseand BYIG phase can exist individually and display very good chemicalcompatibility. Meanwile, the composites present typical ferroelectricityand the addition of BYIG phase did not affect the dielectric loss ofBaTiO3phase. Meanwhile, the composites posses classical soft ferrite, the saturation magnetization (Ms) and initial permeability increaseswith increasing BYIG concentrations. The composites possess highpermeability and low loss in low frequency range. |
PDF Full Text Request