“…5,8,19 A liquid phase is formed instead at a temperature higher than the eutectic temperature. 3,4,14,21,22 The presence of impurity, especially SiO 2 , can lower the eutectic temperature to a temperature ∼1260 • C. 20 The formation of abnormal grains can be suppressed by sintering or annealing * Corresponding author. Tel.…”