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New Luminescent Materials for Energy Saving Light Sources (2010 - 2013)
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ERDF (European Regional Development Fund) supported Research Project

Nr. 2010/0253/2DP/

A place of the project realization: Institute of Solid State Physics, University of Latvia.

A time of the project realization: 01.11.2010. – 31.12.2013.

A sum foreseen for the project realization: 336 000 LVL.

Scientific advisor of the project: Baiba Berzina (dr. hab. phys.)

Motivation. The energy saving is actual around the world. A lot of the generated electric energy is used for the lightening. Therefore an elaboration of new materials which could be used for creating of energy saving light sources including the luminescent lamps (LL) and light emitting diodes (LED) – emitters of white and colored visible light, is actual.

The aim of the project is research of properties for inorganic compounds such as wide band gap nitrides, oxides and related materials (the bulk and nanostructured ones) in order to elaborate new luminescent materials – emitters of white or colored light corresponding to the requirements of energy saving luminescent light sources.

The project realization. Nine activities for the project realization are foreseen, from which six (Nr.2 - Nr.7) are devoted to research of the material. The results obtained are regularly displayed in the progress reports (8 existing reports) as well as published as papers in scientific journals (8 published and submitted papers) and reported in local and international scientific conferences (9 reports).

The results achieved.

Activities Nr.2 and Nr.3. Luminescent properties of AlN and Al2O3 materials differently structured (bulk and nanosize powders – polycrystals) and containing native defects or special dopants (such as Tb or Mn for AlN) and Al2O3 powders with different structures are investigated. It was found that the nanostructured AlN powder mixed with doped AlN:Tb and AlN:Mn powdes under fixed proportions is a prospective material emitting the white light. The powders above are emitting the blue, green and red light, cumulatively producing white light. Luminescence of all these powders can be excited with ultraviolet light from the Hg emission lines at 184 nm and 254 nm thus providing an application of the powder mixture for luminescent lamps. The proportions of the powder mixture are currently worked out.

The second direction of the investigations is devoted to elaboration of composite materials consisting of the powders above and material of the matrixes in which the powders are incorporated. It was found that the PMMA (polymetilmetacrilat) is the best material for incorporation of AlN powders. PMMA material itself is luminescent and under its excitation with Hg emission lines mentioned above a blue emission is observed. This blue light is additional and together with the emission of the mixture of AlN powders is forming white light. Presently the optimal proportions of the components forming the composite material are being worked out.

Activities Nr.4-Nr.7. The following results are observed. The complex oxides undoped and doped with the rare earth elements such as Y2O3-Al2O3 (YAO), ZrO2-Y2O3 (ZYO), CaO-WO3 (CaWO), BaMgAl10O27 (BAM), and SrAl2O4 (SAO) nanocrystals (nanopowders) are synthesized and their luminescent properties are investigated. Investigations are devoted for solving of two problems: i) to obtain a luminescent material for conversion of an ultraviolet or blue light into the white light and ii) creation of the material which is able to accumulate energy under its irradiation with the white light and slowly release this energy as luminescent light during a long time after a cease of the irradiating light. The first problem is related to elaboration of effective new luminescent materials for energy saving white light sources. The second problem is related to creation of materials which can be prospective for the formation of shining caution signs in the place of accident when a supply of the electro energy is interrupted.

It was found that the YAO doped with Ce is prospective material for conversion of blue light into white light. The luminescence spectrum of the material does not contain a blue part but it could be compensating with the blue light illuminated from the exciting source (a blue LED). In the same time, the ZYO doped with Eu and Nb is prospective material for conversion of ultraviolet light into white light. The SAO doped with Eu and Dy is a material, which luminescence continues a long time (5 hours) after a cease of its excitation. Currently production of the transparent luminescent ceramics is worked out, which actual for the technical development of the light sources.

Team of researchers. A team of the researchers consists of 30 members, both experienced and new scientists including the students, being a guarantee for successful implementation of the project tasks.