Electrochemical Synthesis of La-Doped BaTiO₃ Nanopowders.

Electrochemical synthesis has been presented as a powerful technique to produce nanoparticles. However, it has been especially focused on noble metal particles, while few studies have been done on oxides production. On the other hand, when partially doped with trivalent cations at the barium sublattice, BaTiO₃-based ceramics are well known to exhibit semiconductive character, accompanied by a positive temperature coefficient of resistivity (PTCR). Here, we synthesized pure and La-doped BaTiO₃ nanoparticles electrochemically using a metallic titanium electrode as a Ti source. The powder synthesis was made in an electrochemical cell coupled to a thermostatic bath under mild conditions (ambient temperature and pressure) with an electrical potential up to 50 V and current of 3.2 A. In these conditions, the synthesized powders present nanometric size, confirmed by transmission electron microscopy images. The pseudo-cubic BaTiO₃ phase is confirmed by X-ray diffraction and Raman spectroscopy techniques. To check the quality, the powders were sintered at 1250 °C and the ceramics achieved a relative density of 95%. The BaTiO₃:La sintered ceramics present a PTCR jump of up to three orders of magnitude on resistivity with minimum value at room temperature of 10 Ω·cm.