ELECTRICAL-CONDUCTIVITY AND METAL NONMETAL TRANSITION IN THE PEROVSKITE-RELATED LAYERED SYSTEM CAN+1TINO3N+1-DELTA (N = 2, 3, AND INFINITY)

A series of dielectric compounds having perovskite-related structures Ca3Ti2O7, Ca4Ti3O10, and CaTiO3 with the general formulaCan+1TinO3n+1 (n = 2, 3,and∞) showed a metallic conductivity when electron carriers were doped by reduction under H2 atmosphere. The temperature dependence of the metallic resistivity up to 300 K was found to be a linear function ofT2 in a wide temperature region. The system showed a metal-nonmetal transition as a function of temperature below 120 K. An activation type hopping conduction was observed down to a few tens kelvin, and a variable range hopping conduction below that temperature was observed. The electrical transport phenomena of the system showed a strong dependence on the oxygen deficiency δ, but little dependence of the stacking number of the perovskite slabn. © 1992 Academic Press, Inc. All rights reserved.