P. Sarkisov International Laboratory of
Glass-Based Functional Materials
 

 D. Mendeleyev University of Chemical Technology of Russia
 English   
 

Staff of the laboratory

ALBERTO MARIA FELICE PALEARI

Head of the P. Sarkisov International Laboratory for Glass-based Functional Materials,
D. Mendeleev University of Chemical Technology of Russia, Moscow

Professor in Experimental Physics at the Department of Materials Science University of Milano-Bicocca, Italy

RESEARCH ACTIVITY

His research activity is now focused on the physical mechanisms responsible for linear and nonlinear properties in nanostructured glass-based materials. Specifically, the research is mainly devoted to study the effects of crystalline nanophases on photosensitivity, energy transfer mechanisms, optical nonlinearity, and electrically driven light emission.

During his previous scientific activity, he also studied point defects configurations in zirconium and silicon dioxides by means of optical and magnetic resonance spectroscopy, and crystal field effects and exchange interactions in transition metal oxides.

1989-1995

In the field of Zr/Y oxide based materials, he carried out electron paramagnetic resonance (EPR) investigations on electron trap sites, bringing to the structural model of the T-center, which is still the basis of the current studies on the role of the anionic structural disorder and electronic trapping on the properties of zirconia-based materials. [Phys. Rev. B 40, 6518, (1989); Phys. Rev. B 44, 6858, (1991); Phys. Rev. B 49, 9182, (1994); Phys. Rev. B1 51, 15942, (1995)]

1992-2000

He extended his investigation to the class of materials belonging to Ni, Cu, and Mn mixed oxides, by means of EPR and magnetic susceptibility studies. In these systems, he succeeded to clarify the mechanisms responsible for the effects of stoichiometry on exchange interactions and magnetic ordered states. [Phys. Rev. B1 53, 703, (1996); J. Sol. St. Chem. 128, 80, (1997)]

1992-1995

He started to investigate silica-based materials with the aim of clarifying controversial interpretations of the optical properties arising from localized states. In this regards, he contributed to identify the real structure of few coordination defects in SiO2 (1992-1995). He identified EPR signals in irradiated quartz, whose interpretation gave the most detailed description till now of the local configuration on non-bonding oxygen in SiO2. [Phys. Rev. B 49, 9182, (1994), Phys. Rev. B1 52, 138, (1995)]

1995-1998

The fundamental study of the previous period was the basis for the investigation of the role of defect sites on the photochromic properties of silica-based materials. In few detailed works he clarify some debated aspects on the role of Ge doping and native intrinsic defects on the optical activity related to the photosensitivity of Ge-doped silica materials [Phys. Rev. B, 54, 16637, (1996); Phys. Rev. B, 58, 3511,(1998); Phys. Rev. B, 57, 3718, (1998)]

1998-2002

In this period, interesting results were found in Sn- and Ge-doped photorefractive glasses. Among these, it was identified for the first time the Sn-variant of E'-centre in SiO2. This result gave the tool for monitoring and clarifying some of the microscopic mechanisms responsible for the photosensitivity of Sn-doped silica. In oxygen vacancy free Ge-doped silica (produced by an original sol-gel route) he identified the electronic transitions of irradiation-induced Ge sites usually hidden by intense doping-induced oxygen-vacancy absorption bands. [Phys. Rev. B, 58, 9615, (1998); Phys. Rev. B, 60, 2429, (1999); J.Non-Cryst. Sol., 261, 1, (2000); Appl. Phys. Lett., 77, 3701, (2000); Phys. Rev. B, 64, 73102, (2001)]

2001-2012

Since 2001 the activity has been mainly focused to the investigation of nanostructured materials, studying SnO2 nanophases consisting of nanoparticles of few nanometers in size (from 5 to 20 nm and even more, according to the synthesis conditions) embedded in an amorphous silica-based matrix through thermally activated growth from an oversaturated Sn-doped silica gel. The investigations mainly concerned the optical properties arising from quantum confinement of the electronic excitations and the confinement of excitation diffusion within the single nanoparticle, in undoped and rare earth doped materials. The results have been developed showing several interesting properties, such as photosensitivity arising from innovative nanoparticle-driven mechanisms, and sensitized rare earth emission through resonant energy transfer from the nanophase[Phys.Rev.Lett. 90, 055507, (2003); Appl.Phys.Lett. 88, 131912, (2006); Phys.Rev.B 73, 073406, (2006)]. Codoping with erbium ions has also been studied to partially reduce the interface defectiveness thus enabling free-exciton recombination [Appl.Phys.Lett. 89, 153126, (2006)]. Recently, it has been demonstrated the possibility to obtain nanostructured glass designed so as to simultaneously sustain electric currents and charge accumulation in connected but non-conductive branches of the percolation network, thus resulting in electrically tunable dielectric function[Adv.Funct.Mater.20, 3510, (2010)]. From these results his research has been focused on the UV light emission through charge injection and transport in glass-based nanostructured materials. Specifically, recent results give the first demonstration of UV LED fabricated from fully inorganic oxide-in-oxide system [Nature Commun. 3, 690, (2012)]. In this period, his research has also regarded defective and porous silica, and high density varieties of silicon dioxide. In the field of nanostructured materials, he has activated collaboration with the Optoelectronic Research Centre of the University of Southampton, the London Centre for Nanotechnology at the University College of London, the Los Alamos National Laboratory, and the Mendeleev University of Chemical Technology of Russia, in Moscow, where he is Director of the International Laboratory of Glass-based Functional Materials.