Influence of stabilizers on Na-β″-Al2O3 phase formation in Li2O(MgO)-Na2O-Al2O3 ternary systems

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The influences of stabilizers on β- and β″-Al2O3 phase formations in Li2O(MgO)-Na2O-Al2O3 systems were investigated. When stabilized with 4MgCO3·Mg(OH)2·5H2O, most of the β″-Al2O3 phase formed below 1200°C and further β- to β″-Al2O3 transformation with an increase of temperature was not observed. On the other hand, when stabilized with Li2CO3,β″-Al2O3 formation occurred by two steps. First, β″-Al2O3 was partly formed below 1200°C, and, second, noticeable transformation from β-Al2O3 to β″-Al2O3 occurred at higher temperature ranges. It was shown that transient eutectic liquid in the Li2O-Na2O-Al2O3 system promoted the β- to β″-Al2O3 transformation at higher temperatures. Uniform distribution of both Mg2+ and Li+ stabilizing ions enhanced β″-Al2O3 formation at low temperatures. In the Li-stabilized systems, however, homogeneous distribution of Li+ ions hindered both the formation of transient eutectic liquid and the second β- to β″-Al2O3 phase transformation at high temperatures.

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