Papers by Author: Krystyna Wokulska

Abstract: Single crystals of Sr_xBa_1-xNb₂O₆ (0.26 a parameter monotonically increases with increasing of temperature, while the c parameter decreases up to the phase transition temperature T_C, and the next it begins increasing slowly. It was ascertained that with the increase of the Sr concentration in the studied crystals the changes of the lattice parameters were observed. They can be described according to the following relations: a = - 2.418 • 10-5 x² + 1.050 • 10-3 x + 12.479 Å and c = - 0.0015 x + 4.0216 Å. Basing on the obtained results the character of the phase transition was able to do.

Abstract: The high quality Sr0.61Ba0.39Nb2O6 (SBN61) single crystals without any striations were obtained by Czochralski pulling method. The temperature dependence of the lattice parameters of the investigated crystals was studied using a precision X-ray Bond's method. The angular precision of the goniometer 1 arcsine and metric value of Cu K1 (λ = 1.54059292Å) allowed to obtain high precision and accuracy of lattice parameter measurements. The received results allowed to determine the Curie temperature and character of the phase transition in this material. The lattice parameter a monotonically increases and shows hardly visible inflection point at TC when increasing the temperature. The temperature dependence of the lattice parameter c displays quite distinct temperature behaviour. Contrastingly, it decreases with increasing the temperature experiencing an evident anomaly in the vicinity of the structural phase transition point. Obtained value of the ferroelectric phase transition point is TC = 346 ± 3K.

Abstract: Single crystals of composition Sr0.61Ba0.39Nb2O6 (space group P4bm) were prepared using the Czochralski method. The Bond's method of the precise lattice parameter measurements was used to study structure of SBN 61 at room temperature. In this way lattice parameters a = b = 12.45676 ± 6*10-5Å and c = 3.93541 ± 5*10-5Å were determined.