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In this study, tungsten-bronze type materials of Sr2Sm(1-x)NdxTi2Nb3O15 composition (x=0; 0,25; 0,5; 0,75 and 1) were elaborated by classical solid-state reaction. The structural characterization demonstrate that these compounds present tetragonal symmetry, using two space groups P4bm (N°100) and P4/mbm (N°127) respectively. The lattice parameters are a=b≈12,2Ǻ; c≈3,8Ǻ; V≈579,03Ǻ and Z=2. In this compounds, Ti and Nb cations show obvious off-center displacements along the c axis in both the Ti/Nb(1)O6 and the Ti/Nb(2)O6 octahedra. Besides, the unequal Ti/Nb(2)–O bonds length in the equatorial plane of Ti/Nb(2)O6 octahedra indicates the displacement of the Ti/Nb(2) cations in the ab plane, and no displacement of the Ti/Nb(1) cations exists in the ab plane. The results show that this material has two types of octahedral, first octahedron with little deformation around the Ti1/Nb1 and the second octahedron are more distorted around the Ti2/Nb2. The measurements of permittivity and dielectric losses of the ceramic samples performed between 25°C and 700°C (100Hz to 1MHz), high dielectric constants (εr=127 ~ 194) and low dielectric losses (tan(δ) around 10-4 at 1MHz) were found. The maximum value of the dielectric constant is obtained for x=0 (εr=194). The Curie temperature Tc decreases from 332 to 246°C as a function of the substitution of the samarium by neodymium. Detailed microstructural analysis by scanning electron microscope (SEM) and (EDS) for this compounds are also investigated., Moroccan Journal of Chemistry, Vol 8, No 1 (2020)

International audience; In the present study, titanium dioxide and tungsten-modified titanium dioxide photocatalysts were synthesizedby sol–gel method. Structural and morphological characterization has been carried out by using X-ray powderdiffraction (XRD), FT-IR spectroscopy, BET surface area and transmission electron microscopy (TEM)coupled to the energy dispersive spectroscopy (EDX). The adsorption and photocatalytic performances wereinvestigated using two chlorophenoxy herbicides; 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP) as models of organic pollutants in water. The obtained results showthat addition of tungsten to the sol-gel preparation of TiO2 delayed the conversion of anatase to rutile phase.Further increase in tungsten loading apparently stabilized the anatase phase from transformation into inactiverutile. It is also found that, tungsten doped TiO2 exhibited a remarkable enhancement of the photocatalyticactivity compared with the unmodified TiO2 for the photodegradation of the two selected organochlorinesherbicides.