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Synchrotron topographic studies of domain structure in Czochralski grown PrxLa1-xAlO3 crystals
|Krzysztof Wieteska 1, Wojciech Wierzchowski 2, Agnieszka Malinowska 2, Sebastian Turczynski 2, Maria Lefeld-Sosnowska 3, Dorota A. Pawlak 2, Tadeusz Łukasiewicz 2, Carsten Paulmann 4|
1. Institute of Atomic Energy POLATOM, Świerk 05-400, Poland
The real structure of Prx La1-x AlO3 (x = 1, 0.75, 0.55, 0.4 and 0) and LaAlO3 doped with Pr single crystals was characterized with a number of methods including conventional and synchrotron X-ray diffraction topography, and polariscopic micrography. The surface of the samples has been also investigated with a high resolution profilometer.
The crystals were grown by Czochralski technique . High purity Pr6O11, Al2O3 and La2O3 oxides (99.995%) were used as raw materials. All components were mixed in stoichiometric ratios. The pulling and rotation rates were in the range of 1-1.7mm/h and 6-8 rpm. The crystals have been grown in pure nitrogen atmosphere. The samples were cut out perpendicularly to the <100> pseudo-cubic axis closest to the actual growth direction.
The presently applied sample orientation allowed precise recognition of domain systems, and determination of the orientation of the lattice connected with the domains.
It has been confirmed that the domains are of a twin character, similar as it was described by Dudley and Yao in LaAlO3 and LaGaO3 crystals . In those crystals the twin configuration and their changes were studied as a function of temperature in the vicinity of phase transition temperatures .
The domain systems, observed by us, were investigated in PrxLa1-xAlO3 (for different x) and in LaAlO3 crystals doped with Pr , and their appearance and configuration were compared for samples, containing different amount of Praseodymium. The observed twin domains systems were located along <100> and <110> (pseudo-cubic) directions. The evaluated changes of the lattice orientation depend on the chemical composition of the samples. The representative back-reflection white beam synchrotron radiation topograph of the LaAlO3 crystal is shown in Fig.1. The important advantage of the white beam transmission section topography was the possibility of proving that the domain systems are perpendicular to the sample surface (Fig.2).
The details of the domain structure were well revealed in polariscopic micrographs. It was also possible to reveal them by means of the profilometer. The observed surface relief is most probably caused by different mechanical or chemical polishing of differently oriented materials inside the domains.
Figure 1. The representative projection back-reflection topograph of the LaAlO3 revealing the domain structures along two perpendicular planes.
Figure 2. The transmission white beam section topograph of the LaAlO3. The vertical location of the domains proves their perpendicularity to the surface of the sample.
The synchrotron investigations were supported by the HASYLAB project II-20060165 EC.
 S. Turczynski, K. Orliński, D. A. Pawlak, R. Diduszko, J. Mucha, M. Pekala, , J.F. Fagnard, Ph. Vanderbemden, M.A. Carpenter, Cryst. Growth & Design. 11 (2011) 1091-1097.
 M. Dudley, G-D Yao: J. Phys. D: 26 (1993) A120-A125.
Presentation: Poster at IX Krajowe Sympozjum Użytkowników Promieniowania Synchrotronowego, by Agnieszka Malinowska
See On-line Journal of IX Krajowe Sympozjum Użytkowników Promieniowania Synchrotronowego
Submitted: 2011-06-15 13:11 Revised: 2011-09-13 17:17