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Polycrystalline samples of Fe(ND3)2PO4 were prepared by means of a hydrothermal route and characterized using powder x-ray diffraction, scanning electron microscopy, chemical and thermal analysis, magnetic measurements, specific heat and neutron diffraction experiments. This material orders within an orthorhombic (Pnma space group) crystal structure at room temperature, but below 220 K the crystal structure changes towards a monoclinic P 21/n structure through a phase transition with almost no latent heat. Furthermore, the magnetic cell at 2 K is twice the size of the crystallographic cell observed at 80 K. The magnetic structure associated with the Fe(III) ions is thus commensurate with the crystal lattice having a propagation vector , the magnetic moments lying in the yz plane of the crystallographic cell.

Treatment of γ-titanium phosphate with 1 mol dm–3 solutions of MCl (M = Na, K, Cs) results in layered crystalline phases with compositions at 50 °C of: γ-Ti(Na0.5H1.5PO4)(PO4)·H2O, γ-Ti(KHPO4)(PO4)·½H2O and γ-Ti(Cs0.5H1.5PO4)(PO4)·½H2O. Heating at 900 °C gives rise to three-dimensional crystalline compounds. The composition of the new materials depends on the type of alkali-metal present in the solid. The K phase originates KTi2(PO4)3, the Cs phase α-CsTi3P5O19, and the Na phase produces mixtures of NaTi2(PO4)3 and TiP2O7. Moreover, amorphous alkali-metal phosphates which are soluble in acidic media are formed. Samples of γ-Ti(KHPO4)(PO4)·½H2O (A), KTi2(PO4)3(B) and α-CsTi3P5O19(C) have been studied using X-ray powder diffraction. The lattice parameters of A [a= 5.063(3)A, b= 6.297(1)A, c= 11.502(5)A, β= 109.30(4)°], B [a= 8.3569(2)A, c= 23.0725(3)A] and C [a= 6.320(1)A, b= 14.122(2)A, c= 9.333(2)A, β= 105.82(2)°] have also been calculated.

Sodium nitrilotris(methylenephosphonate), Na2[(HO3PCH2)3 NH]1.5H2O, has been synthesized as single crystals and as bulk polycrystalline single phase. This compound is triclinic, space group P 1 , a=7.398(1) A, b=8.446(1) A, c=10.086(1) A, α=81.39(1)°, β=89.29(1)°, γ=81.18(1)°, Z=2 and the structure was solved from single-crystal data. The crystal structure was used to refine the powder diffraction data by the Rietveld method. The structure contains Na4O16 tetramers, with the sodiums cations in distorted oxygen octahedral environments, and molecular units of the acid triphosphonate with protonated nitrogen atom. The framework is three-dimensional with small channels where two types of water molecules are located. This material has also been characterized by thermal analysis, including a thermodiffractometric study, and infrared spectroscopy.

Mixed crystalline tin-titanium phosphates with variable tin-to-titanium molar ratio have been prepared by precipitation of soluble salts of the metal (IV) with phosphoric acid and refluxing the amorphous solids in 17 M H3PO4. The new materials are characterized by chemical textural and thermal analysis and x-ray powder diffraction. The tin-titanium phosphates are solid solutions showing an isomorphic substitution of tin by titanium in the α-tin phosphate lattice and tin substitution in the γ-titanium phosphate lattice. In both cases, the solubility is partial. The coexistence of both saturated phases is observed in samples of composition between the solubility limits.