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首页> 外文期刊>Applied Magnetic Resonance >EPR study of Fe3+- and Ni2+-doped macroporous CaSiO3 ceramics
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EPR study of Fe3+- and Ni2+-doped macroporous CaSiO3 ceramics

机译：Fe3 +和Ni2 +掺杂大孔CaSiO3陶瓷的EPR研究

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Thermally stable macroporous CaSiO3, Fe3+- and Ni2+-doped (0.5 to 5 mol%) ceramics have been prepared by solution combustion process by mixing respective metal nitrates (oxidizers), fumed silica. Diformol hydrazine is used as a fuel. The combustion products were identified by their X-ray diffraction and thermal gravimetry/differential thermal analysis. Single phases of beta-CaSiO3 and alpha-CaSiO3 were observed at 950 and 1200C, respectively. The phase transition temperatures of combustion-derived CaSiO3 were found to be lower compared to those obtained via solid-state reaction method. It is interesting to note that with an increase in the calcination temperature the samples become more porous with an increase in the pore diameter from 0.2 to 8 mu m. The electron paramagnetic resonance (EPR) spectrum of Fe3+ ions in CaSiO3 exhibits a weak signal at g = 4.20 +/- 0.1 followed by an intense signal at g = 2.0 +/- 0.1. The signal at g = 4.20 is ascribed to isolated Fe3+ ions at rhombic site. The signal at g = 2.0 is due to Fe3+ coupled together with dipolar interaction. In Ni2+-doped CaSiO3 ceramics the EPR spectrum exhibits a symmetric absorption at g = 2.23 +/- 0.1. This deviation from the free electron g-value is ascribed to octahedrally coordinated Ni2+ ions with moderately high spin-orbit coupling. The number of spins participating in resonance and the paramagnetic susceptibilities have been evaluated from EPR data as a function of Fe3+ as well as Ni2+ content. The effect of alkali ions (Li, Na and K) on the EPR spectra of these ceramics has also been studied.
机译：通过混合各自的金属硝酸盐（氧化剂），气相法二氧化硅，通过固溶燃烧工艺制备了热稳定的大孔CaSiO3，Fe3 +和Ni2 +掺杂陶瓷（0.5至5 mol％）。二甲酚肼用作燃料。通过X射线衍射和热重分析/差热分析来鉴定燃烧产物。 β-CaSiO3和α-CaSiO3的单相分别在950和1200°C观察到。发现燃烧衍生的CaSiO 3的相变温度低于通过固态反应方法获得的相变温度。有趣的是，随着煅烧温度的升高，样品的孔变得越来越多孔，孔径从0.2增至8μm。 CaSiO3中Fe3 +离子的电子顺磁共振（EPR）谱在g = 4.20 +/- 0.1时显示出弱信号，然后在g = 2.0 +/- 0.1时显示出强信号。 g = 4.20处的信号归因于菱形位点处分离出的Fe3 +离子。 g = 2.0时的信号归因于Fe3 +与偶极相互作用耦合在一起。在掺杂Ni2 +的CaSiO3陶瓷中，EPR光谱在g = 2.23 +/- 0.1时表现出对称吸收。与自由电子g值的偏差归因于具有中等高的自旋轨道耦合的八面体配位的Ni2 +离子。根据EPR数据，已根据Fe3 +和Ni2 +含量评估了参与共振的自旋数和顺磁磁化率。还研究了碱金属离子（Li，Na和K）对这些陶瓷的EPR光谱的影响。

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