Enthalpy of Transformation of a High-Pressure Polymorph of Titanium Dioxide to the Rutile Modification

Science  20 Oct 1967:
Vol. 158, Issue 3799, pp. 388-389
DOI: 10.1126/science.158.3799.388


The enthalpy of transformation of a high-pressure form of titanium dioxide, which has the alpha lead dioxide structure, to the rutile modification was measured by the method of "transposed temperature-drop calorimetry." For the reaction, titanium dioxide (alpha lead dioxide form) transforming to rutile, the change in the heat content is -0.76 ± 0.17 kilocalorie per mole. From this value and the volume change (+ 2.8 percent) associated with the transformation, we estimate the equilibrium pressure at 294°K to be 60 ± 20 kilobars.