Thin film composites in the BiFeO 3 –Bi 4 Ti 3 O 12 system obtained by an aqueous solution-gel deposition methodology

Nanostructure stabilization by low-temperature dopant pinning in multiferroic BiFeO3-based thin films produced by aqueous chemical solution deposition

“…34 Like the other cations, the added Ti 4+ ions are trapped within this network. During the subsequent pyrolysis/ decomposition heat treatments at 260 and 460 1C, the decomposition of the citrate ligands gives rise to the formation of metal oxide bonds, 30 but the temperature is yet too low and the time on the hot plate too short (1 minute steps) that no titanium is susceptible to diffuse out from the BiFeO 3 structure under formation. The last treatment of crystallization consolidates the material, but it does not change the situation meaningfully: Ti 4+ ions are known to have poor inertia to diffuse 53 and the 600 1C/1 h of the consolidation stage still provide not enough energy for them to leave the perovskite lattice.…”

“…According to thermogravimetric analyses this drying + pyrolysis treatment should be done in three different steps: 95 1C/1 min, 260 1C/1 min and 460 1C/1 min. 30 At the end of the eighth deposition-heating sequence, a last hot-plate thermal annealing at 600 1C/1 h is applied to the whole array to crystalize and consolidate the films. Up to 5 films were prepared for each of the six compositions under study and in all cases homogeneous films with uniform morphology and thickness over the entire substrate were obtained.…”

“…To achieve this, thin films with the same optimal formulation already tested in bulk RE 3+ and Ti 4+ co-doped BiFeO 3 have been prepared by an aqueous solution-gel plus spin-coating deposition methodology. [28][29][30] This synthesis approach allows for high control of the stoichiometry, which turns out to be critical to avoid the appearance of chemical gradients 31 and even the formation of the secondary phases mentioned above. Besides, it requires no vacuum conditions nor sophisticated machinery, which, added to the fact that it proceeds in aqueous medium (conventional sol-gel processing and CSD methods alike are routinely based on metalorganic precursors in organic solvents of proven toxicity), 32 further observes environmentally-benign conditions.…”

“…(BNFTO) were prepared by performing an aqueous solution-gel plus spin-coating procedure as described elsewhere. 30 These specific compositions were selected on the basis of different reports in the specialized literature which catalogue them as ideal from the point of view of the multiferroic properties. 5,33 The starting products used for the synthesis were bismuth(III) citrate (…”

Combination of structural and microstructural effects in the multiferroic response of Nd and Ti co-doped BiFeO3 bulk ceramics

“…Finally the third drawback is linked to the existence of a spiral spin modulation which cancels any spontaneous net magnetization in the consolidated material [6]. In order to surmount this adverse scenario different strategies have been attempted, and among them, chemical modification of BiFeO 3 is recognized as a potentially useful approach [7][8][9][10][11].…”