Phase transitions in Sr0.61Ba0.39Nb2O6:Ce3+: II. Linear birefringence studies of spontaneous and precursor polarization
Laboratorium für Angewandte Physik, Gerhard Mercator-Universität,
47048 Duisburg, Germany
2 Institut für Kristallographie, Zülpicher Straße 49b, Universität zu Köln, 50674 Köln, Germany
3 Fachbereich Physik, Universität Osnabrück, 49069 Osnabrück, Germany
Published online: 15 April 2000
The linear birefringence (LB) of (SBN61:Ce) has been measured as a function of temperature within the range of . Large tails have been observed above the ferroelectric phase transition temperatures , 328, 320 and 291 K for the concentrations x = 0, 0.0066, 0.0113 and 0.0207, respectively. Within an Ornstein-Zernike analysis the critical exponents γ, ν and β are determined. It suggests that pure SBN61 belongs to the 3D Ising universality class. Doping with ions, which seem to act as random fields, enhances the relaxor properties. The critical exponents γ and ν of SBN61:Ce shift against those of the three-dimensional random-field Ising model.
PACS: 64.60.Fr – Equilibrium properties near critical points, critical exponents / 77.80.Bh – Phase transitions and Curie point / 77.84.Dy – Niobates, titanates, tantalates, PZT ceramics, etc.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000