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Lanthanide-free amorphous aluminum-borate micropowders: Broadband emitting phosphors for warm-white LED lighting

Seminar Group: 


Alain Ibanez


Institut Néel, CNRS & Université Grenoble Alpes,
Grenoble, France


Tuesday, January 23, 2018 - 2:00pm


MRL Room 2053


Prof. Ram Seshadri

After a brief introduction of Néel Institute and our “Optics and Materials” group, I will present our recent results obtained on original phosphors. These lanthanide-free phosphors are based on glassy aluminum borate powders, without any metal activator as doping, for the development of eco-efficient white-LEDs. They allow producing intense photoluminescence broadbands, extended in the whole visible range, from carbon-related clusters trapped in glassy grains of a few microns in diameters. Thus, from only one phosphor excited with a near-UV LED chip (365- 390 nm), we can generate intense warm white-emissions with promising internal quantum yields around 80-90% and high color rendering indexes (CRI = 92-94). The main objectives of this study is to optimize the chemical compositions, synthesis procedures and thermal treatments for these micrometric powders to enhance their photoluminescence properties. This has been favored by the great versatility of “chimie douce” processes involved for the preparation of these phosphors such as the polymeric precursor method (modified Pechini), or more recently by involving the sol-gel chemistry. Then, the origin of emitting centers has been specified by coupling microcalorimetry, mass spectrometry, thermo- and afterglow-luminescence, NMR, EPR and pulsed ENDOR spectroscopies combined with in progress DFT calculations.