Impurities and Charge Compensation in Some Molybdenium Oxides

Abstract

The role of impurities in the defect formation in MOO, and Na,Mo,O, crystals is discussed. The EPR spectra of the X-ray and uv-irradiation centres are investigated. The constants of the appropriate spin-Hamiltonians are obtained. It is shown that the localization radius of an electron (or a hole) exceeds the interatomic distances, therefore the EPR spectra have a low symmetry with noncoincident axes of the Aand g-tensors. The unpaired density distribution depends on the characteristics of the lattice and impurity cations such as the electronegativity, the coordination number, and the degree of the local environment symmetry distortion.30pOB. YCTaHOBJIeHO , 4 T O PaCnpe~eJIeHHt? HeCIIapeHHOfi CnIIHOBOg IIJIOTHOCTH 3aBHCHT OT CBOfiCTB OCHOBHbIX II IIpHMeCHbIX HaTHOHOB, TaHHX KaK 3JIeKTpooTpHqaTeJIbHOCTb, HOOpHHHaUHOHHOe YHCJIO, CTeIIeHb HCHa?KeHHfI JIOKaJIbHOrO OKpymeHHH Ei OHa B HPIIC-npaKTmecm BcerHa npeBocxoHm MemaToMHBe paccTommfi, B p e 3 y n b~a~e qero qeHTpa1 Tanne. MOO, crystals under certain growth conditions [l]. The defects of that kind were detected, for example, in MOO, crystals grown in H, or 0, atmospheres [2]. The lattice sites and the charge compensation of Fe3+ [3], Cu2+ [l], V4+ 141, and Cr5+ [5] ions in MOO, crystals were examined. There are hole centres in Vand Nb-doped MOO, crystal, too. The interactions with 51V and 93Nb nuclei were observed in their EPR spectra. The number of these defects changes in the course of oxidation or reduction [4]. The same effects were observed in Na,Mo,O, crystals. The numbers of Mo5+ and Cr5+ ions in these crystals depend on the atmosphere of the thermal treatment [6, 71.It was shown that the appearance of electrons in the lattice is due to the decompensation of Me2+ impurity charges on the Na+ sites. The electron density distribution depends on the kind of the impurity cation. This is a general property of all transition metal oxides. The electron localization is different for differently doped crystals as was clearly shown by the experiment for V,05 with a wide set of impurity cations [8].Nat. Makarova 2, 199 164 Leningrad, USSR.23 physica (b) 123/1

Structural, Thermal and Electrical Property of Polycrystalline LaLiMo<sub>2</sub>O<sub>8</sub>

“…Polytungstates and polymolybdates based either on rare earth metals (R = La, Nd, Dy, Sm, Gd etc. [1][2][3][4][5][6][7][8] or alkali metals (Li, Na, K, etc.) [8][9][10][11][12][13] have drawn substantial attention in recent years because of their physical properties such as successive phase transition, ferroelectric/ ferroelastic behavior [1,2], phosphors [3], and ionic conduction etc.…”