This thesis uses solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations to study local structure and disorder in inorganic materials. Initial work concerns microporous aluminophosphate frameworks, where the importance of semi-empirical dispersion correction (SEDC) schemes in structural optimisation using DFT is evaluated. These schemes provide structures in better agreement with experimental diffraction measurements, but very similar NMR parameters are obtained for any structures where the atomic coordinates are optimised, owing to the similarity of the local geometry. The ³¹P anisotropic shielding parameters (Ω and κ) are then measured using amplified PASS experiments, but there appears to be no strong correlation of these with any single geometrical parameter. In subsequent work, a range of zeolitic imidazolate frameworks (ZIFs) are investigated. Assignment of ¹³C and ¹⁵N NMR spectra, and measurement of the anisotropic NMR parameters, enabled the number and type of linkers present to be determined. For ¹⁵N, differences in Ω may provide information on the framework topology. While ⁶⁷Zn measurements are experimentally challenging and periodic DFT calculations are currently unreliable, calculations on small model clusters provide good agreement with experiment and indicate that ⁶⁷Zn NMR spectra are sensitive to the local structure. Finally, a series of pyrochlore-based ceramics (Y₂Hf₂₋ₓSnₓO₇) is investigated. A phase transformation from pyrochlore to a disordered defect fluorite phase is predicted, but ⁸⁹Y and ¹¹⁹Sn NMR reveal that rather than a solid solution, a significant two-phase region is present, with a maximum of ~12% Hf incorporated into the pyrochlore phase. The use of ¹⁷O NMR to provide insight into the local structure and disorder in these materials is also investigated. Once the different T₁ relaxation and nutation behaviour is considered it is shown that quantitative ¹⁷O enrichment of Y₂Sn₂O₇ is possible, and that ¹⁷O does offer a promising future tool for study.

The thesis entitled “Towards the Design of Functional Materials: Evaluation based on Crystal Structure, Photocatalysis and Conductivity Measurements” consist of six chapters. A short introductory note outlines the basis of designing functional materials, different synthetic procedures, characterization techniques and properties such as photocatalysis and ionic conductivity. Chapter 1 describes the effect of Ti doping on photocatalytic activity in orthorhombic perovskite type LnVO3. All the compounds were synthesized by solid state method. Rietveld refinement with high resolution PXRD reveals that the substituent Ti occupies V site rather than Ln Site. Ti substituted compound showed higher photocatalytic activity than the unsubstituted compound and is comparable with that of commercial catalyst. These classes of compounds showed specific degradation towards chlorinated compounds. Chapter 2 discusses the solution combustion synthesis of γ(L)-Bi2MoO6 and its photocatalytic activity under solar radiation. The particle sizes were in the range 300–500 nm with a band gap of 2.51 eV. The degradation of wide variety of cationic and anionic dyes was investigated under solar radiation. Despite the low surface area (<1 m2/g), γ(L)-Bi2MoO6 showed higher photocatalytic activity under solar radiation due to its electronic and morphological properties. Chapter 3 presents a series of visible light photocatalyst M2Ce2O7, synthesized via solution combustion method and characterized by powder X-ray diffraction, solid-state UV-Visible diffuse reflectance spectra, SEM and TEM. The structure of Bi2Ce2O7 has been determined using laboratory as well as synchrotron PXRD. It crystallizes in a disordered F-type structure. The particle sizes are in the range 5–6 nm, band gaps lie within the range 1.7 to 3.2 eV. Bi2Ce2O7 shows high photocatalytic activity, comparable to the commercial Degussa P-25 TiO2 under solar radiation. Chapter 4 examines the effect of Bismuth substitution on crystal chemistry, photocatalysis and conductivity in Sr3V2O8, a variant of palmierite class. These compounds were synthesized by ceramic method and powder X-ray data reveals the limit of the Bi substitution in Sr3-xBi2x/3V2O8 is x=0.4. Single crystal study followed by careful difference Fourier analysis shows that Bi occupies a unique 18h position which is different than Sr1 and Sr2 position. The experimental band gap for Sr3V2O8 was calculated to be 3.45 eV and upon substitution band gap of the material decreases and reaches a value 3.15 eV for the composition x=0.4. Compound exhibits photocatalytic activity specifically towards anionic dyes. However, Bi Substitution leads to lower photocatalytic activity. Chapter 5 describes synthesis, structure, phase transition and ionic conductivity in scheelite type Li0.5Ce0.5MoO4. The compound was synthesized by ceramic method and single crystal study reveals that it crystallizes in the space group I41/a and exhibits conductivity of ~10-3 Ohm-1cm-1 at elevated temperature( 700 °C). It undergoes a first order phase transition around 510 °C. The nature of this transition has been evaluated by laboratory and synchrotron PXRD, DSC, dielectric spectroscopy and variable temperature Raman spectroscopy. The phase transition is shown to be characterized by an iso-structural phase transition which is first example in literature for temperature induced Cowley’s “Type Zero” phase transition. Chapter 6 discusses a new methodology for generating functional materials for fast ion conductors. Several varients of hydrated sodium cadmium bisulfate, Na2Cd2(SO4)3⋅3H2O, Na2Cd(SO4)2⋅2H2O and Na2Cd(SO4)2⋅4H2O have been synthesized and their thermal properties followed by phase transitions have been invesigated. Na2Cd2(SO4)3⋅3H2O (space group P3c). Na2Cd2(SO4)3⋅3H2O loses water completely when heated to 250 °C and transforms to a dehydrated phase (I⎯43d ) whose structure has been established using abinitio powder diffration techniques. Na2Cd(SO4)2⋅2H2O (P21/c) transforms to α−Na2Cd(SO4)2 (space group C2/c) on heating to 150 °C which is a known high ionic conductor. However, when α−Na2Cd(SO4)2 is heated to 570 °C followed by sudden quenching in liquid nitrogen, β−Na2Cd(SO4)2 (P21/c) is formed. β−Na2Cd(SO4)2 takes up water from the atmosphere and gets converted completely to the Kröhnkite type mineral. Further, β−Na2Cd(SO4)2 has a conductivity behavior comparable to α form up to 280 °C, the temperature required for the transformation of β to α form.

Abstract Mineralogical-mineral chemical characterisation of Nb-Ta-bearingassemblages from the Stripåsen granitic pegmatite, NorbergJens Henriksson The occurrence of Nb-Ta-bearing minerals has earlier been briefly documented inthe Stripåsen granitic pegmatite, Norberg, central Bergslagen. This report describesthe background, preparation and basic characterisation of sampled Nb-Ta-bearingmineral assemblages from this pegmatite. These comprise (Y,REE,U,Th)-(Nb,Ta,Ti)-oxides of mainly a tantalum-dominated A 2-m B 2 X 6-w Y 1-n -type, belonging to the pyrochloresupergroup. The major primary mineral is suggested to have been afluorcalciomicrolite, ideally (Ca,Na,☐) 2 Ta 2 O 6 F. In association with abundant fractureformation related to metamictisation of the microlite minerals, they are interpreted tohave been variably altered by late-stage fluids. Thus, the system has beenextensively modified after the primary crystallisation of the pegmatite melt. Besidesthese (Y,REE,U,Th)-(Nb,Ta,Ti)-oxides, monazite-(Ce) ((Ce, LREE)PO 4 ), nativebismuth (Bi) and presumably radiogenic galena (PbS) were identified. The sampleshave mainly been studied by means of scanning-electron-microscopy with energydispersive spectroscopy (SEM-EDS), utilising reflected polarised light microscopy asa complementary tool. The study was done within the framework of the EU-supported FRAME-project which is focused on a selection of metals and minerals,among others niobium (Nb) and tantalum (Ta). / Sammanfattning Mineralogisk-mineralkemisk karakterisering av Nb-Ta-förande associationerfrån Stripåsenpegmatiten, NorbergJens Henriksson Förekomsten av Nb-Ta-förande mineral har tidigare dokumenteras iStripåsenpegmatiten, Norberg, centrala Bergslagen. Här redogörs för bakgrund,provförberedelse och grundläggande karakterisering av provtagna Nb-Ta-förandemineralassociationer från denna pegmatit. Proven som undersökts innehåller(Y,REE,U,Th)-(Nb,Ta,Ti)-oxider av främst tantaldominerad A 2-m B 2 X 6-w Y 1-n -typtillhörande pyroklorsupergruppen. Den huvudsakliga primära fasen tolkas ha varit enfluorkalciomikrolit, idealiskt (Ca,Na,☐) 2 Ta 2 O 6 F. I anslutning till rikligt förekommandesprickor som är relaterade till omfattande metamiktisering har mikroliternaomvandlats i varierande grad av sena fluider. Systemet har alltså förändrats kraftigtefter den primära kristallisationen av pegmatitsmältan. Förutom (Y,REE,U,Th)-(Nb,Ta,Ti)-oxider identifierades monazit-(Ce) ((Ce,LREE)PO 4 ), gedigen vismut (Bi)och vad som sannolikt är radiogen blyglans (PbS). Provmaterialet har huvudsakligenundersökts med genom svepelektronmikroskopi med energidispersiv spektroskopi(SEM-EDS), varvid malmmikroskopi har använts som ett kompletterande verktyg.Studien gjordes inom ramverket för det EU-stödda FRAME-projektet som blandannat fokuserar på förekomster av de kritiska och konfliktrelaterade metallerna niob(Nb) och tantal (Ta).