Yellow pyroantimonates Pb-Sb, Pb-Sb-Sn and Pb-Sb-Zn were synthesized by solid-state reactions at high temperature and characterized by X-ray diffraction and Raman spectroscopy. The lattice size of cubic pyrochlores increases with Sn and Zn doping and with Pb overstoichiometry, indicating the replacement of Sb 5+ by the larger cations. This fact permits the understanding of the corresponding Raman spectral modifications as a consequence of the changes in the local symmetry of the Sb-O polyhedra, justifying the exploitation of Raman spectroscopy to noninvasively identify structural modifications of pyroantimonate pigments in artworks.

The effectiveness of Raman spectroscopy (using a bench-top system on standard pigments) for the characterisation of modified lead antimonate yellows was demonstrated in the already published Part I. The knowledge gained is employed here for the study of yellow glazes on genuine Renaissance plates with the aim of identifying non-invasively lead pyroantimonate compounds by portable micro-Raman equipment. The investigation was carried out directly on site, at the Victoria and Albert Museum (London, UK) and at the Museo Statale d'Arte Medievale di Arezzo (Arezzo, Italy), combining Raman and X-ray fluorescence analyses. In addition to the spectral features of both unmodified Naples yellow and Sn-and Zn-modified lead antimonatecompounds, the Raman patterns related to partially modified pyrochlore structures were observed. For this reason, the possible Sn-induced modification of Naples yellow by cassiterite (SnO 2 ), present within the glaze as opacifier was explored on lead antimonate yellow glaze mock-ups fired at different temperatures.

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The reaction of N-(phosphonomethyl)piperidine and N,N'-bis(phosphonomethyl)bipiperidine with zirconium(IV) in hydrofluoric acid media led to the preparation of two new zirconium fluoride phosphonate derivatives with 1D and 2D structure, respectively. Their structures were solved ab initio from laboratory powder X-ray diffraction (PXRD) data. The monophosphonate derivative, with formula ZrF(2)(HF)(O(3)PCH(2)NC(5)H(10)), has a 1D structure (triclinic, space group P ̅1, a = 6.6484(3) Å, b = 7.1396(3) Å, c = 12.2320(6) Å, α = 77.932(4)°, β = 87.031(6)°, γ = 78.953(5)°, V = 557.22(4) Å(3), and Z = 2) made of inorganic chains constituted from the connection of zirconium octahedra and phosphorus tetrahedra with the piperidine groups bonded on their external part. The diphosphonate derivative, with formula Zr(2)F(4)(HF)(2)(O(3)PCH(2))NC(10)H(18)N(CH(2)PO(3)), has a 2D structure (triclinic, space group P ̅1, a = 6.6243(3) Å, b = 7.2472(4) Å, c = 12.2550(7) Å, α = 102.879(4)°, β = 100.29(1)°, γ = 101.287(7)°, V = 547.03(4) Å(3), and Z = 1) composed of the packing of covalent layers whose structure may be ideally obtained by the joining of adjacent chains of the 1D compound. In these hybrid layers, inorganic regions made of the connectivity of zirconium octahedra and phosphorus tetrahedra alternate with organic regions represented by the bipiperidine moieties. A section dedicated to vibrational spectroscopy analysis is also included, mainly devoted to clarify some issues not easily deducible on the basis of PXRD data and to describe the fluorine environment inside zirconium phosphonate structures.