First-order Raman scattering of A1g and Eg modes originating from the antiferrodistortive F2u soft mode confirms the cubic-tetragonal (Oh-D4h) phase transition in Sr0.993Ca0.007TiO3, at T0=125 K. Within the cubic and the tetragonal phase first-order Raman scattering of the soft ferroelectric F1u mode (TO1) and of the hard TO2 and TO4 optic modes evidences the existence of Ca2+-centred polar microregions. Their size increases rapidly on cooling towards the ferroelectric ordering temperature, Tc=18 K. Splitting and incomplete softening of the F1u components is consistent with an order-disorder transition into an orthorhombic low-temperature phase with C2v symmetry.

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Anomalies in both the linear and the non-linear dielectric permittivity of weakly doped Srl-zCa,TiOs (z = 0.002) and strongly rising dielectric loss in the low-frequency regime evidence coupling of Ca+ + centred polar nanoregions with the predicted coherent quantum state of the host lattice. Glassiness of the nanoregion system is modelled by Lacroix-BBnktype polydispersivity with an extrapolated freezing temperature Tg = 4 K.

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