铬在纳米晶氧化铁中的掺杂研究

Fe^3^+(Cr^3^+)/Fe^2^+混合离子(M^3^+/M^2^+原子比为2:1)共沉淀法制备的Cr~2O~3掺杂量O～14%(质量分数)系列纳米氧化铁，XRDRietveld分析表明全是晶态γ-Fe~2O~3和非晶Fe~2O~3的混合物。非晶丰度范围为21.72%～48.6%。Mossbauer谱分析发现，掺杂量少于2%(质量分数)的氧化铁，晶态和非晶态均是磁性六线谱，大于2%(质量分数)后，另出现强度随掺杂量增加线性递增的超顺磁二线谱。共沉淀过程中，Fe^3^+为主夹杂定量Cr^3^+的Fe^3^+水合配合物网络与Cr^3^+为主夹杂定量Fe^3^+的Cr^3^+水合配合物网络，是形成磁性氧化铁和非晶非磁氧化铁的基础，后者镶嵌在前者中间，阻碍其晶化和晶粒长大，自身形成非晶非磁含铬氧化铁。

Study on the doping mechanism of chromium in nano-sized iron oxide

Nano-sized Fe~2O~3 containing 0～14% (mass fraction) Cr~2O~3 was prepared by coprecipitation method using Fe^3^+ (Cr^3^+)/Fe^2^+ mixed ions (with the ions ratio= 2 : 1). XRD Rietveld analysis showed that such Fe~2O~3 was a mixture of crystalline γ-Fe~2O~3 and amorphous Fe~2O~3. The abundance of amorphous Fe~2O~3 ranged from 21.72% to 48. 60%. When the amount of doping Cr~2O~3 was less than 2.4%, the Mossbauer spectra of either the crystalline or amorphous Fe~2O~3 samples were all sextets. If Cr~2O~3 was more than 2.4%, there appearred a superpara-magnetic doublet whose intensity increases linearly with the concentration of Cr~2O~3 . During coprecipitating, there existed two hydrous complexes, one was Fe^3^+ hydrous complexes mixed with a small amount of Cr^3^+, another was Cr^3^+ hydrous complexes mixed with Fe^3^+. These hydrous complexes formed nano-sized magnetic and non-magnetic Fe~2O~3 respectively. The later hydrous complexes mixed with the former, hinderd crystal forming and growth.