Since the removal of minor phases could not be achieved by leaching, it was tried to prevent the formation of these phases by conducting experiments under argon atmosphere. Therefore, the same experiment was repeated with the same parameters, but in argon atmosphere. However, indications of the occurrence of Reaction (1) such as a rapid heat release and a sudden increase in temperature, which were observed when the same experiment was conducted in air, were not observed when the experiment was conducted in argon atmosphere. XRD analysis further proved that the reaction did not occur. According to these results, another reactant mixture was prepared and the preheating temperature of the pot furnace was increased to 1100 °C instead of 900 °C, however the reaction still did not take place.