Fig xA SEM micrographs of the pellets sintered
Similar behaviour was observed for the La-substituted samples. For Bi0.98La0.02FeO3, higher densities are obtained than for BiFeO3 sintered under the same conditions. Pellets sintered at 700 °C present reflections of metallic Bi, while at 675 °C a phase pure material was obtained. On reducing the sintering temperature to 625 °C and increasing the applied pressure, the density also increased. Experimental conditions and diffraction patterns are shown in the Supplementary data (Table S1 and Fig. S4). For Bi0.93La0.07FeO3, at lower temperatures and higher pressures the quality and density of the pellets are also improved, in such a way that Cytochalasin D on sintering at 650 °C and 75 MPa, the density obtained is sclerenchyma almost the theoretical density (99.1%). If the experiment is carried out at high temperature (800 °C), Bi3+ is reduced to metallic bismuth and Fe3+ is partially reduced yielding magnetite (Fe3O4) (See Supplementary data, Table S2 and Fig. S5). At 675 °C and 70 MPa, the sample is partially reduced again to metallic bismuth and Fe2O3. Therefore, optimal conditions for sintering Bi0.93La0.07FeO3, in terms of purity and density, are 650 °C and 75 MPa. These conditions are also optimal for Bi0.85La0.15FeO3 sintering, with a density of 97.4% (see Table S3 and Fig. S6 in Supplementary data).