Internal Friction in Rutile Containing Ni or Cr

Abstract

Rutile containing Ni gives an internal-friction peak centered near 50°C at 2 kHz characterized by an activation energy E=15.3±2.4 kcal/mole and a characteristic relaxation time r 0 = 3XlO~1 5±1 -7 sec; this peak occurs for tensile stress along [100] or [110]. A peak centered near 200°C with E = 21.4±2.1 kcal/mole and ro=8XlO~1 5±10 sec occurs for stress along [100] but not for stress along [110]. Rutile containing Cr gives similar peaks characterized by E-13.5±2.4 kcal/mole and r 0 = 2Xl0~1 4±1 -6 sec and by £ = 22.2±1.5 kcal/mole and TO=4X10~" 15±0 -9 sec. Light reduction in vacuum decreases the amplitude of the low-temperature peak and enhances the high-temperature peak in both cases. Heavy reduction of rutile containing Cr removes both peaks but they reappear upon subsequent reoxidation. The evidence suggests that the motion of interstitial cations is involved and that reduction causes the formation of a compound defect. A tentative interpretation is given in terms of unpaired Ni 3+ interstitials for the low-temperature peak and of interstitial pairs composed of Ni 3+ -Ti 3+ for the high-temperature peak in Ni-doped specimens; the corresponding peaks in Cr-doped rutile are tentatively interpreted in terms of Ti 4+ interstitials and of interstitial pairs consisting of Ti 4+ -Ti 3+ . It is possible to have two charge-compensating Cr 3 " 1 " on adjacent substitutional sites and preserve the last two models.148 811

Mechanical and thermal properties of ceramics :

“…Drickamer et al [247] review the effect of pressure on the lattice parameters of solids and cite a number of pertinent references. The effect of pressure on the thermal conductivity of a dielectric solid is much greater in the case of solid helium [248][249][250] [251] has surveyed the literature on this increase in the electrical conductivity; I do not know of any experimental thermal conductivity work in this pressure region.…”