CHARGE COMPENSATION OF IMPURITIES AND ELECTRICAL PROPERTIES OF MOO3

An investigation was made of the EPR spectra of MoO3 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 gx = 1.942, gx = 1.953, gx = 1.878, Ax = 32 G, Ay = 69 G. The operator of the hyperfine interaction is of the form (Formula Presented.) The splitting of the transitions with ma ≠ mb 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 3d10. After heating the crystal in air the Cu2+ (3d9) spectrum is observed. The constants of the spin Hamiltonian are: S = 1/2, I = 3/2 gx = 2.087, gy = 2.054, gz = 2.416, Ax = 6 G, Ay = 22.5 G, Az = 93.5 G, Qx = 2.9 G, Qy = 3.0 G, Qz = 5.9 G. Suppositions are made about a reason for the unstability of the electrical conductivity of MoO3 according to the data obtained. Copyright © 1969 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim