Reactions in the System Li 2 O–MgO–Al 2 O 3 –SiO 2 : I, The Cordierite‐Spodumene Join

Phase equilibria along the nonbinary join between cordierite (2MgO · 2Al 2 O 3 · 5SiO 2 ) and spodumene (Li 2 O · Al 2 O 3 · 4SiO 2 ) were investigated in the temperature range 800° to 1550°C. using the quench technique on fourteen compositions. The phase diagram at high temperatures is characterized by a very small region of solid solution on the cordierite side, appreciable solid solution on the spodumene side, and regions of three and four phases toward the center of the system, including liquid, α‐cordierite, mullite, spinel, corundum, and β‐spodumene and its solid solutions. The liquidus has a flat minimum between 40 and 50% cordierite at 1347°, and rises on one side to the congruent melting point of β‐spodumene (1421°) and on the other side to the temperature of complete melting of cordierite (1530°). The lowest temperature at which liquid appears is 1325°. At low temperatures a complete series of metastable solid solutions exists between μ‐cordierite and β‐spodumene. The significance of the data in the preparation of thermal‐shock‐resisting bodies is discussed.