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We present investigations of the domain dynamics and of the evolution of the critical exponent β in a ferroelectric relaxor system, exemplarily in the up-to-date controversial strontium barium niobate (SBN). k-space spectroscopy at the phase-transition and when applying an electric field reveals a size-dependent response of the domains. This is supported by pyroelectric measurements that show, by analysis in terms of criticality, the critical exponent β is not only dependent on the level of poling but also on the manner in which the poling was achieved. It must be concluded that the crystals undergo a phase transition not—as commonly assumed—in a uniform way with homogeneous polarization throughout the crystal. Instead they behave as a set of more or less independent domains with size-dependent stability. Therefore, one should be very careful with critical exponents—especially those derived from experiments that explicitly or implicitly—assume a uniform polarization behavior. [ABSTRACT FROM AUTHOR]

The product of the linear electro-optic coefficient with the electron-hole competition factor r33ζ is determined as a function of the wavelength together with the photorefractive trap density Neff in cerium-doped strontium barium niobate. The photorefractive method of photoinduced light scattering is applied. A pronounced increase of r33 by more than a factor of 2 is self-evident in the blue-green spectral range, which is described by a theoretical approach based on the combination of the Sellmeier formulation and the polarization tensor concept. By this further important material parameters are estimated, such as the strength and frequency of the average dipole oscillator characterizing the optical interband transfer. [ABSTRACT FROM AUTHOR]

We present investigations on temperature-dependent changes in the size distribution of ferroelectric domains in single crystals of the novel tungsten bronze type calcium barium niobate (CBN). Since its congruently melting composition has a relatively high ferroelectric phase transition temperature of about 265 °C, CBN can be considered as an interesting material for various future applications. Using k-space spectroscopy, both unpoled polydomain crystals and crystals poled at room temperature have been investigated in the vicinity of the ferroelectric phase transition. In unpoled CBN, an intermixture of domain-size dependent phase transitions has been observed, which can be described with the model for diffuse phase transitions established by Smolenskii. [ABSTRACT FROM AUTHOR]