Electronic Properties and Defect Structure of Ti₄0₇: Correlation of Magnetic Susceptibility, Electrical Conductivity, and Structural Parameters via EPR Spectroscopy

Variable temperature EPR studies of polycrystalline Ti 4 O 7 and preliminary single crystal studies have been interpreted in relation to the static magnetic susceptibility, electrical conductivity and X‐ray diffraction data obtained on Ti 4 O 7 samples from the same chemical run. This has facilitated the calculation of the mobility, the electrical conductivity, and the electronic effective mass in both the metallic and semiconducting regions of Ti 4 O 7 . Below ≈ 149 K a hopping mechanism dominates the conduction properties and at ≈ 120 K, μ hop ≈ 4 × 10 −6 cm 2 /Vs and σ cal ≈ 1.49 × 10 −3 (Ω cm) −1 . This latter value is in good agreement with σ meas ≈ 3 × 10 −3 (Ω cm) −1 obtained experimentally. An electronic effective mass of 5.6 m e has been obtained for the semiconducting region and is consistent with a value of ≈ 5 m e determined from thermoelectric and Hall effect data for the low temperature phase of Ti 2 O 3 . Above 149 K optical mode phonon scattering and ionized defect scattering combine to yield a total mobility of μ T ≈ 0.6 cm 2 /Vs and σ cal ≈ 1.43 × 10 3 (Ω cm) −1 which is in excellent agreement with the electrical conductivity results at 295 K.