Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 15: Mechanical Properties III
MM 15.5: Vortrag
Montag, 26. März 2012, 16:45–17:00, H 0106
Relaxor properties of pure and cerium doped calcium barium niobate — •Chandra Shekhar Pandey1, Jürgen Schreuer1, Manfred Burianek2, and Manfred Mühlberg2 — 1Institute for Geology, Mineralogy and Geophysics, Ruhr-University Bochum, Germany — 2Institute for Crystallography, University of Cologne, Germany
Lead-free relaxors Sr0.61Ba0.39Nb2O6 (SBN-61) crystallizing in the partially filled tetragonal tungsten bronze (TTB) structure types have attracted much interest because of their outstanding properties. Calcium barium niobate, CaxBa1-xNb2O6 (CBN-x), also belongs to the partially filled TTB structure family having high Tc at ~ 537 K. However, its relaxor behavior have not yet been reported.
We studied the elastic properties of pure and Ce doped CBN-28 (congruently melting; Czochralski grown) between 300K-1503K using resonant ultrasound spectroscopy. The relaxor phenomena for as-grown CBN single crystals was further explored by thermal expansion measurements, which revealed the characteristic temperatures Tb (Burns temperature, initiation of polar naonoregions PNRs), T* (temperature for first freezing of PNRs), and Tm at ~1100 K, ~800 K, and ~600 K, respectively [1]. These findings were confirmed by characteristic elastic anomalies. Cerium doping in pure CBN results in significant lowering of Tc and Tb; however, the intermediate temperature T* remains almost the same [2].
[1] C. S. Pandey, et. al., Phys. Rev. B 84, 174102 (2011). [2] C. S. Pandey, et. al., Appl. Phys. Lett. (Accepted).