Charge Compensation of Impurities and Electrical Properties of MoO 3

An investigation was made of the EPR spectra of MoO 3 single crystals grown in air and in argon. In the crystals grown in air and not specially doped no EPR signal was found. For crystals grown in argon a spectrum is observed due to electrons localized on two different sites of the lattice. This spectrum shows a hfs from a nuclear spin I = 1/2. The spin‐Hamiltonian constants are: S = 1/2, I = 5/2 g x = 1.942, g x = 1.953, g x = 1.878, A x = 32 G, A y = 69 G. The operator of the hyperfine interaction is of the formThe splitting of the transitions with m a ≠ m b is equal to 1/3 A. The splitting by the nuclear spin I = 1/2 is nearly isotropic 3 to 4 G. The same spectrum is observed in air‐grown crystals after irradiation with a quartz‐mercury lamp. In copper doped crystals grown in argon the copper is found to be in the state 3d 10 . After heating the crystal in air the Cu 2+ (3d 9 ) spectrum is observed. The constants of the spin Hamiltonian are: S = 1/2, I = 3/2 g x = 2.087, g y = 2.054, g z = 2.416, A x = 6 G, A y = 22.5 G, A z = 93.5 G, Q x = 2.9 G, Q y = 3.0 G, Q z = 5.9 G. Suppositions are made about a reason for the unstability of the electrical conductivity of MoO 3 according to the data obtained.