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Sr0.5Ba0.5Nb2O6/Ni0.8Zn0.2Fe2O4-based Magnetoelectric Composite Ceramics

Author: LiYongJiang
Tutor: ChenXiangMing
School: Zhejiang University
Course: Materials Science
Keywords: Magnetoelectric effect Dielectric relaxation Composites Microstructures
CLC: TB332
Type: Master's thesis
Year: 2006
Downloads: 119
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Abstract


Magnetoelectric effect refers to the material under the external magnetic field electrode and an external electric field to produce the phenomenon of induced magnetization. Magnetoelectric effect in magnetic materials can achieve mutual conversion between magnetic and electric fields, is expected to be applied to the sensors, micro-displacement transducer and magnetoelectric memory. In order to obtain a new system of magnetic materials with greater magnetoelectric effect, of the basic rules of design based on the magneto-electric material proposed structure of tetragonal tungsten bronze relaxor ferroelectric Sr 0.5 Ba 0.5 Nb 2 O 6 ferroelectric phase as a composite of new ideas to obtain large magnetoelectric effect. This method breakthrough in the design of composite magnetic materials in the ferroelectric phase confined to the limitations of the perovskite structure. This experimental system to study the structure of tetragonal tungsten bronze relaxor ferroelectric Sr 0.5 Ba 0.5 Nb 2 O 6 < / sub> cubic spinel structure of ferromagnetic Ni , Zn , 0.8 0.2 Fe 2 O 4 coexist composite magnetic electric ceramic dielectric, magnetic and electric properties. Prepared by solid-phase sintering (1-x) Sr , Ba , 0.5 0.5 the Nb 2 O 6 / xNi 0.8 Zn 0.2 Fe 2 O 4 (x = 0,0.1,0.2,0.3,0.4 and 0.5) dense ceramic. Throughout the sintering process, Sr 0.5 Ba 0.5 of Nb 2 O 6 and Ni , 0.8 Zn 0.2 the Fe 2 O 4 two-phase mutual coexistence between the two does not react chemically to produce impurity or intermediate phase. Dense sintered ceramics by oxygen annealing good polarization and magnetization and magnetoelectric effect observed. When the ferroelectric phase Sr 0.5 Ba 0.5 Nb 2 O 6 content of 70mol% magnetoelectric ceramic composite having a maximum magneto-electric coupling coefficient, 26.6mV/cm/Oe, far higher than the maximum magnetic-electric coupling coefficient obtained in the composite magnetic dielectric ceramic single phase material. Sr 0.5 Ba 0.5 Nb 2 O 6 / Ni 0.8 Zn 0.2 Fe 2 O 4 magnetoelectric effect in composite magnetic ceramics with a strong component of sensitivity, temperature sensitivity, and frequency sensitivity, so by Changing the composite ceramic micro-structure of the composition and preparation process to improve the magnetoelectric coupling coefficient. On the other hand, Sr 0.5 Ba 0.5 Nb 2 O 6 / Ni 0.8 the zn 0.2 Fe 2 O 4 composite ceramics considerable magnetoelectric effect, at the same time has a the extrinsic dielectric relaxation and contrast giant dielectric constant. When an electric field is applied on the material surface, the space charge will accumulate around the interface between the two phases due to the two-phase different conductivity, thereby generating high apparent dielectric constant, which explore new giant dielectric material opens up a possible new way. OF use the equivalent RC circuit analysis and interpretation of the impedance characteristics of the composite ceramic to a similar Debye relaxation dielectric anomalies observed in the analysis of the dielectric. The dielectric constant of the samples showed a strong component of the sensitivity and frequency sensitivity, with the the ferromagnetic phase Ni 0.8 Zn 0.2 the Fe 2 O 4 content increases or reduced frequency of testing, the dielectric constant of the ceramic composite will increase rapidly. At room temperature to 100 ℃, 0.7Sr 0.5 Ba 0.5 Nb 2 O 6 / 0.3Ni 0.8 Zn 0.2 the Fe 2 O 4 samples, measured at 100kHz permittivity (ε '~ 3500 ) showed good

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