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Synthesis, crystal chemistry, and physical properties of new mixed-metal perovskite-related oxides

Thesis/Dissertation ·
OSTI ID:7021054

The goal of this work is to synthesize and characterize multiple-B-cation perovskite-related compounds (A[prime] [sub 1[minus]x]A[double prime][sub x]) (B[prime] [sub 1[minus]y]B[double prime] [sub y])O[sub 3[minus]z], that are structurally and chemically related to high-temperature cuprate superconductors. High-temperature superconductors have two common features (1) copper-oxygen CuO[sub 4/2] nets (layers) separated by inorganic metal-oxide spacer layers and (2) formal mixed valency of copper or a mechanism of charge transfer between the copper-oxygen and space layers. To achieve structural similarity, that is, to provide distinct CuO[sub 4/2] and B[double prime] O[sub 4/2] layers, two synthetic strategies were developed, one for stoichiometric and the other for nonstoichiometric mixed-metal oxides. To develop and refine the strategies, La[sub 2]CuSnO[sub 6], La[sub 2[minus]x]M[sub x]CuSnO[sub 6[minus]x/2+[sigma]] (M = Ca, Sr, Ba), Ba[sub 2]La[sub 2]CuSn[sub 2]O[sub 11], Ln[sub 2]CuMO[sub 6] (Ln = lanthanide; M = Mn, Ti, Ir, Sn), [La[sub 0.86][open square][sub 0.14]Cu[sub 3]] (Ti[sub 3.42]Al[sub 0.58])O[sub 12], Ca[sub 2]LaMn[sub 1.1]Al[sub 0.8]Cu[sub 0.1]O[sub 7], and Ca[sub 2]LaMnMO[sub 7] (M = Al, Ga, Fe) were synthesized. The compounds were characterized by diffraction techniques, susceptibility measurements, and other physical property measurements. The substitution chemistry, crystal chemistry, redox chemistry, and structure property-relationships of the layered cuprates, La[sub 2]CuSnO[sub 6], La[sub 2[minus]x]M[sub x]CuSnO[sub 6[minus]x/2+[sigma]] (M = Ca, Sr, Ba), and Ba[sub 2]La[sub 2]Cu[sub 2]Sn[sub 2]O[sub 11], were studied in detail. The copper stannates are antiferromagnetic semiconductors and remain so regardless of chemical modification. Study of the compounds has demonstrated that the physical and chemical characteristics of the inorganic spacer layer determine structure-property relationships and control superconductivity.

Research Organization:
Northwestern Univ., Chicago, IL (United States)
OSTI ID:
7021054
Country of Publication:
United States
Language:
English

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