**4. Conclusion**

The mixed oxides modified route (solid-state reaction) is a direct alternative to obtain highly densified BSTx ceramics. In this route, the high-energy ball milling and the applied heat treatment allowed the preparation of nanometric powders (less than 200nm) with Perovskite-type structure ABO3. The Curie temperature of the BSTx ceramics was unambiguosly determined as a function of temperature by several techniques: Raman spectroscopy, differential scaning calorimetry, and measurements of dielectric constant. This temperature was succesfully tuned from 87 K to 400 K by varying the Sr/Ba ratio, as expected. However, a shifting in the orthorhombic to tetragonal phase transition was observed in the sintered ceramics. For instance, the OTPT for the BST0-BST2 samples was shifted down 17-27 K with respect to the literature. The origin of this shifting is probably residual stresses associated to the fine-grained microstructure of the sintered samples.

The group of BST0, BST1, BST2 and BST3 ceramics present P(E) curves with ferroelectric behavior at room temperature. The other cases present paraelectric behavior. Moreover, the BST0, BST1and BST2 samples present rather low maximum and remanent polarization and coercive fields. BSTx ceramics (x = 0, 1, 2, 3) displayed piezoelectric response in the contact resonance piezoresponse force microscopy mode (CR-PFM). The polycrystalline BSTx ceramics showed ferroelectric domains with sizes several times smaller than the grains.
