Synthesis, structure and properties of some transition metal oxides

Transition metal oxides possess optical, electric, dielectric, magnetic, thermal, catalytic and many other properties with fascinating structure-property relations.; For the transparent p-type conducting oxides CuScO2+ y, CuSc1-xMg xO2 and CuSc1-xMg xO2+y the limits of x and y were determined. Structural studies using neutron diffraction data established the position of the intercalated oxygen. Compositions with low y were found to first gain oxygen and then lose oxygen when heated in air.; Zinc oxide powders prepared by peroxide and nitrate decomposition show the evidence of holes in the O 2p band by iodometric titrations and the presence of nitrogen in nitrate-derived samples by chemical analysis. Complex impedance spectra were used to determine the electrical conductivity of these powders.; The high dielectric constant in "SrCu3Ti4O 12" and the giant dielectric constant in CaCu3Ti 4O12 are rationalized on a barrier layer mechanism. Our study on ceramic samples showed that the conductivity in the conducting regions is related to Ti on Cu sites, and the insulating barriers are between the crystallites in "SrCu3Ti4O12" but within the crystallites in CaCu3Ti4O12. Confirmation was obtained by complex impedance measurements on a CaCu 3Ti4O12 crystal.; Spintronics is an emerging technology that combines electronics with magnetics through the manipulation of electron spins. We find that on application of a magnetic field to La2NiMnO6 there are significant changes in its electrical resistance and dielectric constant below 280 K. Our neutron diffraction studies on La2NiMnO6 confirm that it is ferromagnetic below 280 K.; Negative thermal expansion of the O-Cu-O linkage was found in CuMO 2 (M = La, In, Sc, Al) delafossite compounds by Rieveld analysis of neutron diffraction data. The behavior was especially strong for CuLaO 2 (alpha = -6.3 x 10-6/K) and CuScO 2 (alpha = -4.5 x 10-6/K) up to 600 K. This is an unusual example of strong negative thermal expansion in a metal oxide based on an O-M-O linkage instead of an M-O-M linkage.; Orthorhombic beta-AgAlO2 was prepared by an ion-exchange reaction. The structure was characterized by neutron powder diffraction and all the positional parameters were reported for the first time. Structural systematics of tetrahedral MM'X2 compounds were carefully examined.