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# Structural and magnetic characterisation of some mixed metal oxides and oxyhalides

Stephens, Deborah Ann (2011)
Ph.D. thesis, University of Birmingham.

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## Abstract

This thesis investigates the structural and physical effects of changing the ratio of Mn:Ga in the anion deficient perovskite, YSr$$_3$$Mn$$_{4-x}$$GaxO$$_{10.5}$$. YSr$$_3$$Mn$$_{4-x}$$GaxO$$_{10.5}$$ crystallises in the tetragonal space group I4/mmm, with lattice parameters a~7.64 Å and c~15.66 Å. Magnetic characterisation indicates that the material is antiferromagnetic overall, with ferromagnetic ordering in the [001] direction of the unit cell. Earlier work on the structural analogue, Y$$_{1.07}$$Sr$$_{2.93}$$Mn$$_{2.67}$$Ga$$_{1.33}$$O$$_{10.5}$$, identified a magnetic peak in the neutron diffraction pattern that could not be fitted following refinement of NPD data. This work concluded that the extra peak was due to a small MnO impurity. The effects of oxidation and fluorination on the structural and physical properties of YSr$$_3$$Mn$$_{4-x}$$Ga$$_x$$O$$_{10.5}$$ with various Mn:Ga ratios are investigated. The physical and structural effects of substituting Mn$$^{3+}$$ or Co$$^{3+}$$ for Fe$$^{3+}$$ in the perovskite related material, Pb$$_4$$Fe$$_3$$O$$_8$$Cl, have been investigated using XRPD, NPD and magnetic susceptibility measurements. An earlier characterisation of Pb$$_8$$WO$$_{10}$$Cl$$_2$$ suggested a deficit on all atom sites within the unit cell. This work suggests a different structure with an intact cation and main oxygen sub-lattice. The site of an additional oxygen was established linked to tungsten. Pb$$_8$$WO$$_{10}$$Cl$$_2$$ crystallises in space group I4/mmm, with a = 3.9846(2) and c = 22.690(2) Å.

Type of Work: Ph.D. thesis. Greaves, Colin (Professor) Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Chemistry TP Chemical technologyQD Chemistry University of Birmingham 1512
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