"Nanocomposites and nanomaterials"

XRD studies of the precursor thermal decomposition in the production of nanopowders LaLuO3:Yb3+ with a perovskite type structure
Shyrokov O.V.1, Lobunets T.F.1, Chudinovych O.V.1,2, Ragulya A.V.1,2
1 Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine.
Krzhizhanivskoho Str., 3, Kyiv-03142, Ukraine.
E-mail: shyrokovav@gmail.com
2 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”.  Prospect Peremohy, 37, Kyiv-03056, Ukraine.

Since the invention of the first laser with a polycrystalline active medium in 1964 [1], scientists have been constantly searching for ways to improve its performance, requiring the development and research of new materials with given properties.
The process of structure formation evolution during thermal decomposition of the precursor synthesized by precipitation in obtaining complex perovskite type oxide phases in La2O3-Lu2O3-Yb2O3 system was observed by X-ray diffraction using the powder method. Two main steps were found. The first one is related to the amorphous structure: the decomposition of the complex chemical compound formed after the precipitation and its internal rearrangement, and the second one to the formation and accumulation of the perovskite crystalline phase.
X-ray spectra of the samples obtained at temperatures up to 700°C at the first stage of the decomposition contain two broad diffuse peaks (halo) at 22-38° and 38-70°. In the interval of precursor's thermal decomposition temperatures from 120 to 700°C the processes of complex compound decomposition and internal rearrangement take place. An amorphous powder is formed with a gradual increase in the atomic ordering, evidenced by a decrease and a qualitative change in the background. Possibly ordered domains typical for REE carbides, hydrides or carbohydrides are formed in the amorphous matrix.
With further increase in temperature the second main stage of decomposition begins. The process of formation and accumulation of the perovskite crystal phase is not uniform. At 750-780 °C the size of crystallites of the perovskite type phase LaLuO3:Yb3+ rapidly increases, after which the growth slows down.

1.	Hatch S.E., Parsons W.F., Weagley R.J. Hot-pressed polycrystalline CaF2:Dy2+ laser // Appl. Phys. Lett. -1964.-V.5.- P. 153-154.