Synthesis of low-density γ-Al_2O_3 from high-density α-Al_2O_3 in the presence of LiBO _2 melt under high pressure

摘要

In general, the high-density state is a preferred state of materials under high pressures. In this study, however, when the LiBO_2Al _2O_3 system quenched from melts at the cooling rate of 5060 °Cs under high pressures, low density γ- Al_2O_3 was synthesized from high density α- Al_2O_3, with a 7.1 volume expansion of Al_2O_3. While those samples which are quenched at the same cooling rate under a lower pressure appeared to be glassy. The minimal pressure synthesized the low-density γ- Al _2O_3 or the maximal glass forming pressure was decreased with increasing content of Al_2O_3 below its saturation point in LiBO_2 melt.