Synthesis and characterisation of novel metal pyrophosphates

[摘要] 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.

[发布机构] University:University of Birmingham;Department:School of Chemistry

[关键词] Q Science;QD Chemistry