Abstract This study presents the effect of Er 3+ substitution for Fe 3+ at low concentrations on the structural, magnetic, and magnetostrictive properties of cobalt ferrite synthesized by sol–gel method using spent Li-ion batteries as raw materials. The XRD results confirm the formation of pure-phase cubic spinel structure with average crystallite sizes of 24.8–41.5 nm as obtained through the Scherrer formula. Although Er 3+ substitution does not show any observable changes in morphology, the magnetic and magnetostrictive properties are strongly affected. Density measurements obtained by the Archimedes method reveal that the bulk density decreases and the porosity increases with Er 3+ substitution because of the formation of intragranular pores during sintering. The saturation magnetization and coercivity of the samples obtained with a vibrating sample magnetometer are influenced by the incorporation of Er 3+ at the B-sites. Magnetostriction and strain derivative curves show that Er 3+ substitution makes cobalt ferrite more suitable for advanced magnetomechanical stress sensors and energy-efficient actuator devices.

中文翻译：

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Er 3+ 取代对废锂离子电池合成铁氧体钴的结构、磁性和磁致伸缩性能的影响

摘要 本研究展示了低浓度下 Er 3+ 取代 Fe 3+ 对以废锂离子电池为原料通过溶胶-凝胶法合成的钴铁氧体的结构、磁性和磁致伸缩性能的影响。XRD 结果证实了纯相立方尖晶石结构的形成，其平均晶粒尺寸为 24.8-41.5 nm，如通过 Scherrer 公式获得的。虽然 Er 3+ 取代没有表现出任何可观察到的形态变化，但磁性和磁致伸缩特性受到强烈影响。通过阿基米德方法获得的密度测量结果表明，由于在烧结过程中形成了粒内孔，体积密度随着 Er 3+ 取代而降低，孔隙率增加。用振动样品磁强计获得的样品的饱和磁化强度和矫顽力受在 B 位掺入 Er 3+ 的影响。磁致伸缩和应变导数曲线表明，Er 3+ 取代使钴铁氧体更适用于先进的磁机械应力传感器和节能致动器装置。