Lanthanum influence on the structure, dielectric properties and luminescence of BaTiO3 ceramics processed by spark plasma sintering technique

Nano-sized lanthanum doped barium titanate Ba1-xLaxTiO3 (0.00 ≤ x ≤ 0.08) powders were prepared by sol-gel method. These powders with perovskite BaTiO3 cubic single phase structure, obtained after calcinations of gels precursors at 1100 °C, 3 h in air, were pressed and sintered by spark plasma technique in order to obtain dense ceramics. The optimal sintering temperatures used for Ba1-xLaxTiO3 powders were dependent on lanthanum amount added to barium titanate and decrease from 1300 °C to 1160 °C when the La concentration increases from 0 to 8 at.% La. An additional annealing treatment was made in air at 900 °C for all the sintered pellets for oxidize and remove the contaminant graphite which migrated in ceramics from the graphite die during the sintering process. The effect of lanthanum concentration on the densification behavior, structure, microstructure, photoluminescence and dielectric properties of the Ba1-xLaxTiO3 ceramics was investigated in this work. The results shown that as the lanthanum content increases, the grain size of the powders and ceramics increases accompanied by decrease of density of the samples. Also, increase of La amount inserted in BaTiO3 lattice leads to significant decrease of the dielectric losses and Curie temperature and, increase of dielectric permittivity but the luminescence properties seem to be less affected.