Structural and magnetic characterisation of some mixed metal oxides and oxyhalides

This thesis investigates the structural and physical effects of changing the ratio of Mn:Ga in the anion deficient perovskite, YSr₃Mn_4-xGaxO_10.5. YSr₃Mn_4-xGaxO_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_1.07Sr_2.93Mn_2.67Ga_1.33O_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 YSr₃Mn_4-xGa_xO_10.5 with various Mn:Ga ratios are investigated. The physical and structural effects of substituting Mn³⁺ or Co³⁺ for Fe³⁺ in the perovskite related material, Pb₄Fe₃O₈Cl, have been investigated using XRPD, NPD and magnetic susceptibility measurements. An earlier characterisation of Pb₈WO₁₀Cl₂ 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. Pb₈WO₁₀Cl₂ crystallises in space group I4/mmm, with a = 3.9846(2) and c = 22.690(2) Å.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

2011

Author dc:creator

• Stephens, Deborah Ann

• TP Chemical technology
• QD Chemistry