预烧和烧结温度对Sr_3Co_2Fe_(24)O_(41)铁氧体微结构及性能的影响

采用固相反应法制备Sr3Co2Fe24O41六角锶铁氧体粉末,探究了预烧和烧结温度对材料电阻率的影响。随预烧温度上升,材料的主晶相由M相转变为Z相,在预烧温度1200℃获得了纯净的Z相;烧结温度为1150℃时,材料晶粒为均匀的片状,具有较大电阻率。烧结通O2条件的实验表明,进气量变化时(20~40L/h),材料的电阻率变化不大,改变O2分压(0.2~0.4MPa)时,在0.3MPa时获得了最大的电阻率,其值为1.12×109?·cm。最后,在室温下测试了材料对施加弱磁场的磁电效应(0~500m T),结果表明Z型铁氧体与M型六角铁氧体相比在室温弱场下具有明显的磁电效应,M型的介电常数则几乎无变化,而Z型铁氧体在0~100m T下介电常数下降,变化率为1.6%。改变测试频率,在200k Hz测试时获得了较大的磁电效应。

Influences of calcination and sintering temperatures on microstructure and properties of Sr3Co2Fe24O41 materials

Sr3Co2Fe24O41 hexagonal ferrites were prepared by solid-state reaction method, and influence of presintering and sintering temperatures on their properties was investigated. As the presintering temperature rises, the main phase of the material changes from M-type to Z-type and at 1200℃ the pure Z-phase is obtained. The sintering temperature 1150℃ was determined, at which the uniform planar grains with high resistivity were compounded. Then the sintering condition of O2 was analyzed, and the results show that the resistivity is mainly depended on the partial pressure of the O2(0.2 to 0.4MPa), but not the O2 flowing amount (20 to 40L/h), and at 0.3MPa the resistivity can reach 1.12G?·cm. At last the magnetic dielectric property was tested under the weak magnetic field (0 to 500mT) at room temperature. The results show that the magnetic dielectric effect of Z type is more obvious than that of M type hexagonal ferrites. No changes of the permitivity was founded on the M type material and the permitivity of the Z type decreases in the magnetic field of 0 to 100mT with the change rate of the permitivity about 1.6%, at the frequency 200kHz the change rate of the permitivity is a little more than that at the other frequency.