Synthesis and characterisation of novel metal pyrophosphates

Baker, Annabelle R. (2014). Synthesis and characterisation of novel metal pyrophosphates. University of Birmingham. Ph.D.

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This thesis describes the synthesis, properties and structural characterisation of Mg\(^2\)\(^+\), Mn\(^2\)\(^+\)and Ti\(^4\)\(^+\) pyrophosphates and Li and V substituted analogues.
α and β polymorphs of MgH\(_2\)P\(_2\)O\(_7\), were isolated by a novel acid melt synthetic route. Both polymorphs crystallised in monoclinic space groups, with α-MgH\(_2\)P\(_2\)O\(_7\) isostructural with NiH\(_2\)P\(_2\)O\(_7\) and β-MgH\(_2\)P\(_2\)O\(_7\) isostructural with CaH\(_2\)P\(_2\)O\(_7\). Rietveld refinements of NPD data gave excellent fits to both structural models. MgLi\(_0\)\(_.\)\(_8\)H\(_1\)\(_.\)\(_2\)P\(_2\)O\(_7\)was also isolated with Rietveld refinement suggesting two similar possible structural models.
MnH\(_2\)P\(_2\)O\(_7\), a structural polymorph of β-MgH\(_2\)P\(_2\)O\(_7\) was also synthesised via a similar route. Magnetic analysis revealed MnH\(_2\)P\(_2\)O\(_7\) to be paramagnetic, with a small antiferromagnetic component. Incorporation of Li was again achieved via the addition of lithium carbonate during synthesis. Rietveld refinement of NPD data suggests a similar structure to that of MnH\(_2\)P\(_2\)O\(_7\) and a composition of MnLi\(_0\)\(_.\)\(_5\)H\(_1\)\(_.\)\(_5\)P\(_2\)O\(_7\).
A metastable polymorph of TiP2O7 has been successfully synthesised at low temperature and adopts a structure similar to the ideal cubic structure. Incorporation of vanadium resulted in an expansion of the unit cell. Both phases undergo a phase transition above 275°C to the ideal cubic structure. Addition of vanadium results in an unusual uniform spherical morphology unseen in parent phase.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Chemistry
Funders: None/not applicable
Subjects: Q Science > QD Chemistry


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