Diplomamunka feladat a Fizikus mesterképzési szak hallgatói számára

A hallgató neve: Quang Thien Tran specializációja: Fizikus MSc - nukleáris technika
A záróvizsgát szervező tanszék neve: NTI
A témavezető neve: Dudás Zoltán
- munkahelye: Wigner Research Centre for Physics
- beosztása: Research fellow
- email címe: dudas.zoltan@wigner.mta.hu
A konzulens neve: Czifrus Szabolcs
- tanszéke: NTI
- beosztása: Director of Institute of Nuclear Techniques
- email címe: Czifrus.Szabolcs@reak.bme.hu
A kidolgozandó feladat címe: Effect of bi- and trivalent doping ions, on the sol-gel derived zinc silicate structural properties
A téma rövid leírása, a megoldandó legfontosabb feladatok felsorolása:

Zing silicate (Zn2SiO4) is also known by its mineral name Willemite. Willemite is one of the important class of crystalline luminopheres with a rhombohedral crystalline structure. Traditionally, the Willemite based materials were synthesized by solid state reaction starting from inorganic oxides mixtures as raw materials. The high synthesis temperature (1200-1400 0C) necessary for this method limited its utilization. Lately several methods were developed with lower energy consumption and higher purity of the obtained Willemite based luminescent material. Among these methods was the sol-gel technique, which implies precursor mixtures at molecular level and significantly lowering the required thermolysis temperatures, (700-900 0C) in order to develop the desired Willemite pure crystalline phase. Willemite has been identified as an ideal host matrix for many rare earth ions but the structural evolution of the resulted materials are poorly understood. We propose to obtain, characterize and understand some Mn2+ and/or Ce3+ , or Eu3+ and/or Tb3+ activated Willemite phosphors derived from sol-gel process. The influence of different charge compensators (Li+ and K+), the amount of the activators, the thermal treatment temperature will be also studied.

The main goal of the research, by means of a combined structural refinement using X-ray and neutron diffraction measurements, to determine the structural modification induced in Willemite crystalline network as result of doping with Mn2+ , Eu3+ , Tb3+ and Ce3+ activators, with or without charge compensators. From the neutron diffraction data we can get information about the light atoms and their surroundings, distortion of the crystalline structure and the extent of lattice distortions. The X-ray diffraction measurements give precise data concerning the lattice parameters and the minor crystallographic phase. We expect that the comparative studies of the Neutron and X-ray diffraction and time of flight neutron scattering outcome would lead to a more comprehensive understanding of structural properties evolution and other processing variable relation to emission mechanism exhibited by our synthesized materials. Also combined neutron diffraction (ND) and Time-of-flight neutron diffraction (TOF-ND) measurements could improve the knowledge regarding crystalline structure, especially when some allusive structures are developed, like mesocrystallinity.

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*A témavezető jelen feladatkiírás aláírásával tudomásul veszi, hogy a BME TVSZ 145. és 146.§ alapján az egyetem a képzési célok megvalósulása érdekében a szakdolgozatok, illetve diplomamunkák nyilvánosságát tartja elsődlegesnek. A hozzáférés korlátozása csak kivételes esetben, a dékán előzetes hozzájárulásával lehetséges.
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