Synthesis in Confined Space of Undoped and Eu(III)-doped Yttrium Vanadate Phosphors

The objective of this thesis is to assess and evaluate the effects of the space confinement, given either by the miniemulsion’s droplets or by the pores of a mesoporous material, on the nucleation and crystallisation of a target inorganic crystalline matrix, i.e. non-substituted and Eu(III)-substituted yttrium vanadate. To do that, the properties of the material (i.e. composition, structure, morphology, and photoluminescence) obtained within the confined space framework will be compared to the properties of the same material synthesised through classical, non-confined processes. The batch synthesis will be considered as opposed to miniemulsion synthesis, as regards the wet chemistry synthesis, while the synthesis in mesoporous materials (through wet incipient impregnation) will be exploited as synthesis in confined space to be compared to the solid-state approach. The possible noted differences will be likely related to the spatial confinement of the reactions. Yttrium vanadate, both non-substituted and Eu(III)-substituted, is chosen as model inorganic matrix as it possesses good luminescent properties and a very efficient energy transfer to the lanthanide ions, properties that make it a worldwide used matrix to obtain red phosphors. Moreover, studies have proved that the crystallisation of this matrix proceeds through an amorphous intermediate (cfr. Ostwald’s step rule), making it possible to follow the crystallisation process via photoluminescence measurements, which may enable to deepen the knowledge of its crystallisation pathway. Within the work of this thesis, non-substituted and Eu(III)-substituted yttrium vanadate will be synthesised both via inverse miniemulsion approach and through the synthesis in mesoporous materials. Since the photoluminescence properties depend on the structure and morphology of the product, the size, size distribution, shape, crystallites size and crystalline phase of the obtained nanoparticles will be analysed and related to the photoluminescence properties measured for each product, and the possible differences compared to classical synthesis will be highlighted.