Iron oxidation state effect on the Mg-Al- Si-O glassy system

Impact of the pulling rate on the redox state and magnetic domains of Fe-Si-O glass ceramic processed by LFZ method

“…Among them, laser floating zone (LFZ) method was found as a powerful processing technique enabling to prepare not only the glass-ceramic materials [7] but also high-quality single crystals [18][19][20], eutectic J o u r n a l P r e -p r o o f structures [3,[21][22][23] and highly oriented polycrystalline materials [23][24][25][26]. Moreover, by providing conditions for a self-supported molten zone, the LFZ method has merit over other high-temperature synthesis approaches to avoid contamination and impurities resulted from high-temperature interaction with crucibles or other materials [27]. On the other hand, LFZ method allows us to deeply study phase transformation kinetics [7,[28][29][30][31], tuning the states of the redox-active cations diffusion phenomena [30][31][32] and crystallization/vitrification mechanisms in the glass fibres [27,28].…”

“…Moreover, by providing conditions for a self-supported molten zone, the LFZ method has merit over other high-temperature synthesis approaches to avoid contamination and impurities resulted from high-temperature interaction with crucibles or other materials [27]. On the other hand, LFZ method allows us to deeply study phase transformation kinetics [7,[28][29][30][31], tuning the states of the redox-active cations diffusion phenomena [30][31][32] and crystallization/vitrification mechanisms in the glass fibres [27,28]. Previous investigations have addressed the significant impact the chemical composition, the ambient atmosphere, composition, pulling rate on the shape, phase composition, morphology and the related characteristics of the samples grown by LFZ method [27][28][29][30][31][32].…”

“…On the other hand, LFZ method allows us to deeply study phase transformation kinetics [7,[28][29][30][31], tuning the states of the redox-active cations diffusion phenomena [30][31][32] and crystallization/vitrification mechanisms in the glass fibres [27,28]. Previous investigations have addressed the significant impact the chemical composition, the ambient atmosphere, composition, pulling rate on the shape, phase composition, morphology and the related characteristics of the samples grown by LFZ method [27][28][29][30][31][32]. Furthermore, it is suggested that the crystallization during the LFZ processing, strongly depends on the thermal gradient near the melt/solidification interface and the pulling rate [26].…”

“…However, understanding of the clustering and nucleation process accompanied by relevant microscopic and macroscopic changes imposed by temperature gradients during the LFZ procedure still is very inconclusive and challenging. Previously studies had revealed that the incorporation of up to 8% (in mol%) iron oxide into the magnesium aluminosilicate (MAS) glass fibres prepared by LFZ method only presents paramagnetic attribute at room temperature likely due to poor clustering of the nano-sized iron oxide species and huge directional crystallization of non-magnetic components [27]. Moreover, it was demonstrated that even through Mossbauer spectroscopy, the estimation of the Fe 3+ /Fe 2+ ratio in the above-mentioned glasses is hardly attainable because of the strong overlap of the sextets due to Fe 2+ and Fe 3+ in the iron oxides clusters [7].…”

“…From these studies [7,27] it was found that only above 8% mol of Fe, magnetic phases of iron clusters, are formed in the glass matrix. Therefore, in the present work, 10Fe2O3-90SiO2 glass fibres were grown using the LFZ method.…”