【摘要】 应用溶胶-凝胶技术制备纳米钡铁氧体,研究不同的制备工艺对钡铁氧体生成过程的影响。研究结果表明:在工艺中,500℃预处理5h后的试样需经水洗除杂工艺才可以在Fe/Ba=11.2、900℃退火4h的条件下制得高纯度BaFe12O19(简称BaM)磁性材料,其磁性能为:比饱和磁化强度Ms=68.6A·m2·kg-1,剩余磁化强度Mr=25.6A·m2·kg-1,矫顽力Hci=29.95×103A/m;而工艺中,由于未引入杂质Na+,所以简化了工艺步骤,即不需水洗工艺,但需适当地延长干胶预处理时间(>5h)和退火时间,即可在Fe/Ba=11.4,900℃退火6h的条件下,制得单相BaM磁性材料,其比饱和磁化强度Ms=70.12A·m2·kg-1,矫顽力Hci=31.26×103A/m。更多还原

【Abstract】 Refs.5 and 7 proposed a method for synthesizing ultrafine barium ferrite (BaFe₁₂O₁₉) by sol-gel technique that is excellent except that, in our opinion, they used ammonia as precipitating agent. We found experimentally that NaOH is better than ammonia except that a new problem is brought in, i.e., it brings in unwelcome sodium ions. In this paper we present a method that employs NaOH as precipitating agent without bringing in unwelcome sodium ions. BaFe₁₂O₁₉ nanoparticles were prepared for using sol-gel technique. Influence of preparation process on formation process of barium ferrite was studied. Experimental results show that, after the gel had been preheated at 500℃ for 5 h and washed by water to eliminate sodium ions and then heat-treated at 900℃ for 4 h, we could get high purity nanoparticles of BaFe₁₂O₁₉ with a coercive force of 29.95×10³A/m, and a specific saturation magnetization M_s of 68.6 A·m²·kg^-1 with Fe/Ba=11.2. By selecting a different Fe/Ba and prolonging preheating and heat-treating time, we found it possible to make washing away sodium ions with water unnecessary. After the gel had been preheated at 500℃ for 6 h and then heat-treated at 900℃ for 6 h, we could get high purity nanoparticles of BaFe₁₂O₁₉ with a coercive force of 31.26×10³ A/m, and M_s=70.12 A·m²·kg^-1 with Fe/Ba=11.4. Besides, M_s=70.12 A·m²·kg^-1 is superior to M_s=62.7 A·m²·kg^-1 and M_s=65 A·m²·kg^-1 attained by products of Japanese firms Toshiba and Toda respectively.更多还原