High-pressure electrical resistance, compressive strength, and non-stoichiometry of titanium dioxide

Abstract

Single crystals of TiO 2 (rutile) were studied for electrical resistance at pressures up to 100 kbars at 20 °C in the [100]and [001]directions using a “belt”-type high-pressure device. For single crystals pressed from I to 6.5 kbars an initial maximum slope of dR/dP = −0.2 × 10 4 Ω bar −1 was found. From about 6.5 to 100 kbars, a slope of dR/ dP = −0.08 Ω bar −1 was determined. No appreciable anisotropy in electrical resistance on single crystals of TiO 2 in the [100]and [001]directions was obtained for rutile with c a = 0.64 . The compressive strength of rutile was determined from high pressure experiments and from measurements using an Instron machine. For single crystals, a compressive strength ranging from 8.0 to 9.4 kbars was determined at room temperature. High-pressure heating and cooling studies on single- and polycrystalline TiO 2 upto 45 kbars and 1600 °C were undertaken to determine phase stability of rutile. X-ray diffraction data and chemical analyses on high pressure hot-pressed specimens showed only the rutile phase with the composition ranging from TiO 1·86 to TiO 1·91. Polycrystalline rutile specimens with essentially theoretical density were obtained by high-pressure hot-pressing and slow cooling. The electrical resistivity on high-pressure TiO 2 ranged from 0.1 to 1.8 × 10 3 Ω-cm .