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Basics of Growth Techniques Used for Bulk Single Crystals of Transparent Semiconducting Oxides
Published in Zbigniew Galazka, Transparent Semiconducting Oxides, 2020
In principle, this is a modification of the Czochralski method with a similar growth furnace concept, as demonstrated in Fig. 1.11. In the Kyropoulos method a crystal is grown on a seed by a slow cooling down of the melt substantially with no pulling up of the crystal, although very small pulling rates (smaller than that in the Czochralski method) and crystal rotation can also be applied. The growth proceeds inside the melt until substantially the whole melt is crystallized on the seed, after which the crystal is cooled down to room temperature. The Kyropoulos method requires very low temperature gradients in the melt and efficient heat dissipation, which is produced at the growth interface during liquid–solid phase transition. Technically, this is achieved by a furnace design with a possible cooled seed rod and crucible bottom, and heated crucible wall, typically inductively, although a resistance heating can be applied as well. It requires suitable adjustment of temperature gradients to control the growth rate and minimize fast solidification of the melt. The Kyropoulos method enables large crystal volume with the diameter close to a crucible diameter. Alternatively, the melt may freeze on the seed being in a contact with the crucible wall. Thermal insulation and crucible materials, as well as the growth atmosphere, are typically the same as those used for the Czochralski method, depending on the compound to be grown and its melting point.
An Assorted Outlook on the Versatility of Thermoluminescence Techniques
Published in Sanjay J. Dhoble, B. Deva Prasad Raju, Vijay Singh, Phosphors Synthesis and Applications, 2018
Sumedha Tamboli, S. J. Dhoble, B. C. Bhatt
The Kyropoulos method was developed for growing large alkali halide crystals by the German scientist Spyro Kyropoulos. After that large sapphire crystals were also grown by using this method. In this technique, first a melt is formed and then seed introduction is done. The melt is raised through a temperature gradient to form a single crystal. The single crystal will grow from the point where the seed comes in contact with the melt [78].
Thermal and dielectric properties of ferroelectric lead germanate single crystals doped with chromium ions (Pb5Ge3O11:Cr3+)
Published in Phase Transitions, 2018
U. Bachulska, J. Jankowska-Sumara, A. Majchrowski, M. Chrunik, D. Zasada, A. Soszyński
Pure PGO single crystals were grown using Czochralski method [8], while Cr3+-doped PGO crystals were obtained by means of Kyropoulos method [9]. For XRD characterization small pieces of obtained crystals were crushed and ground thoroughly in the agate mortar until they turned into very fine, uniform powder samples. The diffraction patterns of PGO and PGO:Cr3+ (0.2%) crystals were collected using the BRUKER D8 Discover diffractometer with CuKα radiator (λKα1 = 1.54056 Å, 40 kV and 40 mA) with Göbel FGM2 mirror. The Bragg-Brentano diffraction geometry was applied. The diffraction angle 2θB ranged from 15° to 80° with a step of 0.01° and acquisition time of 2 s per step. All the measurements were done at 298 K in the temperature-stabilized Anton Paar HTK 1200N chamber. For the data processing the DIFFRAC.SUITE EVA application was used. The phase analysis was done with support of the Crystallography Open Database (COD). For Rietveld refinement [10] and calculations of precise unit cell parameters, the FullPROF ver. 3.00 program was used. The reference Crystallographic Information File (CIF) of PGO phase used for refinement was received from the supplementary data given in [11].