Yttria Doping and Sintering of Submicrometer‐Grained α‐Alumina
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Abstract:
The sintering behavior of α‐alumina powders doped with magnesia (500 or 1500 ppm) and yttria (0, 500, or 1500 ppm) was investigated using constant‐heating‐rate dilato‐metric experiments. The apparent activation energies for the intermediate stage of sintering were 740, 800, and 870 kJ/mol for 0, 500, and 1500 ppm yttria doping levels, respectively; these were independent of magnesia doping. Yttria‐doped powder compacts exhibited systematic anomalous second peaks in the densification rate curves at certain grain sizes which were determined only by yttria doping levels. Before the anomalous peak, with lower yttrium contents at grain boundaries, yttrium in an atomic state delays densification and raises the apparent activation energy. Beyond the peak, with higher yttrium contents at grain boundaries, yttria‐rich precipitation delays the densification. Within the peak, yttrium segregation near the saturation level enhances densification.Keywords:
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Alkoxide
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LiF-YF3 extraction agent used to extract yttrium metal not only effectively reduced oxygen content and calcium content in yttrium metal,but also reduced content of fluorinion in yttrium metal.Results show that purityof yttrium reaches 99.35wt%,the purity of the metal yttrium is effectively improved.
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