Ti^4+掺杂M型六角铁氧体BaFe12–xTixO19陶瓷的磁学和介电特性

Magnetic and Dielectric Properties of Ti^4+-doped M-type Hexaferrite BaFe12–xTixO19 Ceramics

六角铁氧体由于其具备高温下的低场磁电耦合特性,有望应用于新型多态存储器及磁电传感器等微电子器件。利用Ti^4+离子对M型六角铁氧体BaFe12O19进行B位掺杂,不仅可以调控材料的磁结构和磁学特性,同时,Ti离子在六角铁氧体B位的不等价掺杂还可以产生相关缺陷、载流子和变价Fe离子进而改变其电学特性。本研究采用固相烧结法制备了M型六角铁氧体BaFe12–xTixO19(x=0,0.5,1,1.5)陶瓷,并对其进行了性能表征和测试,研究了B位Ti^4+掺杂对材料结构、磁学和介电特性的影响。研究结果表明,BaFe12–xTixO19呈现上、下自旋反平行的亚铁磁序。当Ti^4+离子掺杂量较低时,更易取代位于上自旋格子的Fe3+离子,其磁化强度随Ti掺杂量的增加而减小;随着Ti4+离子掺杂量的进一步增加,位于下自旋格子的Fe^3+离子也会逐渐被取代,此时,饱和磁化强度随掺杂量的增加而增加。此外,Ti^4+离子的引入也会使晶粒内部呈现半导性,在晶粒/晶界处产生Maxwell-Wagner界面极化,故而M型六角铁氧体BaFe12–xTixO19陶瓷会出现明显的低频介电增强并伴随着Maxwell-Wagner介电弛豫。

Hexaferrite system is expected to be applied in various kinds of multi-state memories,magnetoelectric sensors and other new microelectronic devices,due to its high temperature magnetoelectric coupling effect with low field.Not only the B-site doping of M-type hexaferrite BaFe12O19 with Ti^4+ion can change its magnetic structure and magnetic properties,but also the defects,multivalent Fe ions,introduced by B-site non-epuivalent Ti doping,could affect its electric properties.In this study,M-type hexaferrite BaFe12–xTixO19(x=0,0.5,1,1.5)ceramics were prepared by solid phase sintering.The effects of Ti^4+doping on the structural,magnetic and dielectric properties were studied.The results show that BaFe12–xTixO19 is in ferrimagnetic order with antiparallel spins.When the doping concentration of Ti^4+ions is low,it tends to replace Fe^3+ions with up-spin.And the magnetization decreases with the increase of Ti dopant.However,with the further increase of Ti^4+doping,Fe3+ions with down-spin is also replaced,and the saturation magnetization increases with the increase of x.The introduction of Ti^4+ions can also make the grains to be semiconductor,which results in the Maxwell-Wagner interface polarization behavior at the interfaces between semiconducting grains and grain-boundaries.Hence,M-type hexaferrite BaFe12–xTixO19 ceramics appear obvious low frequency dielectric enhancement accompanied by a Maxwell-Wagner dielectric relaxation.