Preparation of phase pure, dense fine grained ceramics by conventional and spark plasma sintering of La-substituted BiFeO3 nanoparticles

High density ceramics of the system Bi1−xLaxFeO3, 0 ≤ x ≤ 0.15, have been prepared starting from nanoparticles obtained by mechanosynthesis. The ceramics have been sintered conventionally at 850 °C and by spark plasma sintering (SPS). Sintering conditions have been optimized to obtain single phase ceramics, and the microstructure of the ceramics has been compared. Ceramics prepared conventionally present grain sizes from 5 μm to less than 1 μm, whereas grain sizes by SPS are in the range from 50 to 100 nm, which demonstrates that it is possible to obtain nanostructured ceramics of La-substituted BiFeO3 using mechanosynthesis followed by SPS at low temperature (625-650 °C). The as-prepared SPS ceramics show low resistivity, indicating some reduction in the samples. However, after an oxidative anneal in air, ceramics are highly insulating at room temperature and electrically homogeneous. The high quality of the ceramics has also been demonstrated by XRD, EDX, Raman and DSC.