Immiscibility Area in the System TiO 2 –ZrO 2 –SiO 2

A furnace for use in conjunction with the X‐ray spectrometer was developed which was capable of heating small powdered specimens in air to temperatures as high as 1850°C. This furnace was also used for the heating and quenching of specimens in air from temperatures as high as 1850°C. An area of two liquids coexisting between 20 and 93 weight % TiO 2 above 1765°± 10°C. was found to exist in the system TiO 2 –SiO 2 , which is in substantial agreement with the previous work of other investigators. The area of immiscibility in the system TiO 2 –SiO 2 was found to extend well into the system TiO 2 –ZrO 2 –SiO 2 . The two liquids were found to coexist over a major portion of the TiO 2 (rutile) primary‐phase area with TiO 2 (rutile) being the primary crystal beneath both liquids. The temperature of two‐liquid formation in the ternary was found to fall about 80°C. with the first additions of ZrO 2 up to 3%. With larger amounts of ZrO 2 the change in the temperature of the boundary of the two‐liquid area was so slight as to be within the limits of error of the temperature measurement. Primary‐phase fields for TiO 2 (rutile), tetragonal ZrO 2 , and ZrTiO 4 were found to exist in the system TiO 2 –ZrO 2 –SiO 2 . SiO 2 as high cristobalite is known to exist in the system TiO 2 –ZrO 2 –SiO 2 .