Lahcen Bejjit

EPR study, in the normal and superconducting states, of GdBa2Cu3O7 single crystal before and after grinding

Abstract Electron paramagnetic resonance (EPR) at various temperatures (300–4 K) is reported for the superconducting single crystal ( T c ≅90 K), before and after grinding. In the normal state ( T > T c ), the EPR line from the single crystal is isotropic and asymmetrical due the skin effect. On the contrary in the superconducting state ( T T c ), characterised by a non-resonant signal just below T c and by the noise on the spectrum, the EPR line is symmetrical and anisotropic. The grinding of crystal allowed us to avoid some of these complications. After grinding the skin effect is eliminated and the line becomes symmetrical. The temperature dependence of the EPR line width shows a Korringa-type interaction between Gd 3+ moments and the conduction electrons in the normal state, and an important broadening below 20 K announcing a magnetic order of the Gd 3+ at low temperature; but the origin of the line width narrowing appeared between 90 and 20 K is not clear. The line intensity varies with temperature as the Curie–Weiss law in the normal state. Below T c it decreases, when the temperature is lowered from T c , as result of the reducing of the volume producing the EPR signal.

PIXE ANALYSIS OF MOROCCAN ARCHITECTURAL GLAZED CERAMICS OF 14TH-18TH CENTURIES

The PIXE analysis of glazes and ceramic bodies of a set of architectural glazed ceramics (mostly the zellige mosaics), sampled from seven Moroccan monuments from the 14th to the 18th century AD, has been performed. We have identified high lead glazes, opacified with tin-oxide, laid over a calciferous body to produce hard tiles easy to chisel as required by the zellige technique. The analysis has revealed significant differences between the monuments examined: in particular in the formulation of the base glass and in the use of stains to produce coloured glazes. We observed the peculiarity of materials used in Marrakech and we could distinguish, both in terms of glazes and ceramic bodies, the two almost contemporary Madersas dedicated to the sultan Bou Inan, one in Meknes the other in Fez. The PIXE measurements integrate a broad range of spectrometric investigations performed in the past few years.

Zelliges from Dar‐El Beïda Palace in Meknes (Morocco): Optical Absorption and Raman Spectrometry

Abstract Samples of zelliges, from the Dar‐El Beïda Palace built in Meknes (Morocco) in the 18th century, were studied by optical absorption and Raman spectroscopies. The results obtained by the two techniques were in agreement and show that the glazes of the zelliges are lead oxide–rich in composition. Other phases were also detected, mainly the SnO2 cassiterite opacifier for the white glaze, and heamatite (α‐Fe2O3) in association with magnetite Fe3O4 and manganese oxide (MnO2) for the brown glaze. For the blue and green glazes, the elements responsible for the coloring are cobalt (Co2+) and copper (Cu2+), respectively.

On-site XRF characterization of archaeological materials in CERA center of Rissani (Morocco)

Different glazed ceramics and glass artifacts, coming from the excavations of the Sijilmassa site and exhibited in CERA (center for Alaouite studies and research) in Rissani (Morocco), were analysed by portable X-ray fluorescence spectrometry. All glazed ceramics are lead glaze and their ceramic bodies are calcareous clay. Glass objects are different nature: lead-glass, lead-lime-alkaline and potassium-lime glass. Classical elements were used to colour glaze and glass: tin for white, cobalt ore for blue, copper for green, manganese and iron for black and iron for yellow.