Refractometric study of polar ordering in Sr1−xBaxTiO3single crystals

The temperature variations of the index of refraction were studied in nominally pure SrTiO3, Sr1−xBaxTiO3 single crystals (x = 0.02, 0.05, 0.07 and 0.14) and in Sr1−x CaxTiO3 (x = 0.014). Contributions of the spontaneous electrooptical effect to the temperature variations of the refractive index allowed us to obtain the concentration and temperature variations of the spontaneous polarization. It is shown, that the concentration dependence of the spontaneous polarization in Sr1−xBa.TiO3 has no significant peculiarities near the critical concentration xc = 0.035 and belowxX = 0.07 the polarization is proportional to (X — Xg)1/2, where xg = 0.0027. Contrary to that the precursor polarization increases, when x goes down to xc .