Understanding complex functional oxides by Raman scattering: some examples

In questo lavoro di tesi viene utilizzata la spettroscopia Raman per studiare le caratteristiche e le proprietà di tre classi di ossidi funzionali: ossidi ad alta entropia (in particolare \ch{(CoCuMgNiZn)O}), nanoparticelle di zinco-ferriti con struttura a spinello (sia pure \ch{ZnF2O4} che drogate con gallio e magnesio) e niobati di ferro (\ch{FeNb11O29}) in celle elettrochimiche. Abbiamo dimostrato che la spettroscopia Raman è uno strumento molto potente per investigare proprietà quali l'omogeneità, la stabilità strutturale e il grado di inversione. Queste, inoltre, sono strettamente correlate ad altre caratteristiche utili a fini applicativi.

This thesis work is aimed to the study of some relevant properties in functional oxides by means of Raman spectroscopy. Among functional oxides three case studies have been treated: \ch{(CoCuMgNiZn)O} High Entropy oxide, very hot-burning material, \ch{ZnF2O4}, a spinel-type ferrite and the iron niobate \ch{FeNb11O29}. Functional oxides are materials that combine considerable applicative interest with the possibility of exploring microscopic mechanisms of considerable interest for basic physics. The operating parameters of these systems depend on the intrinsic properties of the constituents and on how these properties are modified or tuned according to the different methods of preparation and the post-conditioning. We have demonstrated that Raman spectroscopy is a powerful tool to investigate the properties such as the homogeneity, the structural stability, and the inversion degree which are strictly correlated to the other properties exploitable for application purposes.