P. Brovetto

Radioluminescence investigation of Nasicon materials

The X-ray excited luminescent emissions of samples of Nasicon (NASuper-Ionic-CONductor) compounds of different stoichiometries were recorded vs. wavelength in the 280 to 560 nm range. The spectra show main peaks near 300 nm, with wavelengths and intensities depending on the sodium content of samples. These peaks are ascribed to radiative recombinations of electron-hole pairs trapped by Frenkel defects caused by the displacement of sodium ions in lacunar sites. Analysis of the recorded spectra highlights the effect of stoichiometry on ionic conductivity.

On electron pairing in unconventional superconductors

Abstract:This paper presents a study whose aim is to decide whether the basic mechanism of electron pairing is the same for all unconventional superconductors such as perovskites, cuprates, organic compounds and alkaly-stuffed fullerene. By analyzing the features of these dissimilar materials, arguments are singled out showing that superconduction is originated by electrons combined in weakly bound pairs running in regions bordering on certain lattice discontinuities which are common to the structure of the superconductors dealt with. Special attention is devoted to the properties of the YBCO cuprate.

Study of defects inZr lacunar Nasicon crystals

SummarySamples of Nasicon compounds NaxZr2-ySi3-zPzO12, withx - 4y +z = 4, were investigated by radioluminescence and thermoluminescence experiments. It has been found that disorder in the Zr lacunar sublattice originates charged defects active as centres of electron-hole radiative recombinations in excited crystals. The analysis of radioluminescent spectra shows that the minimum displacements of Na+ ions exceed 5 Å. This result yields information on the paths of Na+ ions in the ionic conduction of these materials. PACS 61.72.Ji - Point defects (vacancies, interstitials, color centers, etc.) and defect clusters.

On the lattice defects in Nasicon compounds

SummarySamples of Nasicon compounds (Na super ionic conductor) with different silicon and phosphorus contents were investigated by performing radioluminescence experiments. In all samples examined, the Frenkel pairs, originated by the displacements of sodium ions in lacunar sites, were found to be the dominant defects. Some useful information on sodium ion mobility was obtained from the analysis of radioluminescence spectra.