通过采用机械合金化方法制备的高活性的粉体,可以高度可重复性地制备高质量的铁基超导材料Sm0.85Nd0.15FeAsO0.85F0.15.样品具有高临界温度Tc(约51 K)和高临界场Hc2(达到377 T).由WHH公式确定的Hc2显著高于常规固相方法制备样品的典型值 (＜200 T).高的临界磁场Hc2与样品微结构有很大关系.机械合金化处理的原始粉体包含大量的晶格畸变缺陷,在快速升温和低温退火制备的小晶粒陶瓷样品中这些缺陷会部分残留,因此形成有效的磁通钉扎,从而提高样品的临界场.
High quality iron-based superconductors of Sm0.85Nd0.15FeAsO0.85F0.15 were reproducibly synthesized from highly reactive powders prepared by mechanical alloying method,The samples show Tc around 51 K,with an upper critical field (Hc2) up to 377 T determined from WHH formula,which is much higher than those found in the samples prepared from conventional solid state reactions (＜ 200 T),The high Hc2 is closely correlated with its microstructure.It is proposed that the mechanically alloyed raw materials contained high densities of lattice distortions,which were partially maintained during rapid heating and low temperature sintering,thus contributing to flux pinning in the final fine-grain ceramics.
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