A comparative study on the effect of additives ( $$\text {Bi}_{2}\text {O}_{3}$$ and $$\text {ZrO}_{2}$$ ) and sintering temperature on structural, morphological and magnetic properties of M-type barium hexaferrite has been investigated. Oxalate precursor method was used to synthesize $$\text {BaFe}_{12}\text {O}_{19}$$ in the present investigation. Additives $$\text {Bi}_{2}\text {O}_{3}$$ and $$\text {ZrO}_{2}$$ of 1 wt% were added to some part of the calcined powder and sintered at 1100 °C and the remaining powder was sintered at three different temperatures (1100 °C, 1200 °C and 1300 °C). A significant variation in the crystallite and grain sizes of the samples was noticed both as a function of sintering temperature and nature of additives. Insights of hysteresis loops hinted the redistribution of Fe $$^{3+}$$ ions towards octahedral sites, resulting improvement in saturation magnetization with sintering temperature and decrease in coercivity is attributed to an increase in grain size. Incorporation of $$\text {Bi}_{2}\text {O}_{3}$$ and $$\text {ZrO}_{2}$$ in $$\text {BaFe}_{12}\text {O}_{19}$$ leads to decrease of coercivity, squareness ratio but an improvement was evident in saturation magnetization and remanence, and these are explained based on the redistribution of Fe $$^{3+}$$ ions. The distribution of Fe $$^{3+}$$ ions towards octahedral sites was estimated theoretically and compared with experimental magnetic moments with least possible error. Occupancy of Fe $$^{3+}$$ ions in tetrahedral and octahedral sites was further confirmed using Rietveld refinement which shows that $$\chi ^2$$ values are in the acceptable range.

中文翻译：

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Bi2O3 和 ZrO2 添加剂和烧结温度对六铁酸钡中阳离子分布的作用：Neel 亚晶格理论的估计

添加剂（$$\text {Bi}_{2}\text {O}_{3}$$ 和 $$\text {ZrO}_{2}$$ ）和烧结温度对合金的影响比较研究已经研究了 M 型六铁氧体钡的结构、形态和磁性能。本研究采用草酸盐前体法合成$$\text {BaFe}_{12}\text {O}_{19}$$。将 1 wt% 的添加剂 $$\text {Bi}_{2}\text {O}_{3}$$ 和 $$\text {ZrO}_{2}$$ 添加到部分煅烧粉末中并在 1100°C 下烧结，剩余的粉末在三个不同的温度（1100°C、1200°C 和 1300°C）下烧结。注意到样品的微晶和晶粒尺寸的显着变化是作为烧结温度和添加剂性质的函数。磁滞回线的洞察暗示 Fe $$^{3+}$$ 离子向八面体位点重新分布，随着烧结温度的升高，饱和磁化强度的提高和矫顽力的降低归因于晶粒尺寸的增加。$$\text {Bi}_{2}\text {O}_{3}$$ 和 $$\text {ZrO}_{2}$$ 并入 $$\text {BaFe}_{12} \text {O}_{19}$$ 导致矫顽力、矩形比降低，但饱和磁化强度和剩磁有明显改善，这些都是基于 Fe $$^{3+}$$ 离子的重新分布来解释的. Fe $$^{3+}$$ 离子在八面体位置的分布是从理论上估计的，并与实验磁矩进行比较，误差最小。Fe $$^{3+}$$ 离子在四面体和八面体位点的占有率使用 Rietveld 精修进一步证实，这表明 $$\chi ^2$$ 值在可接受的范围内。