? Multiferroic properties of Ti-doped BiFeO3 ceramics

Synthesis, microstructure and properties of BiFeO₃-based multiferroic materials: A review

“…For example, whereas some works assert an enhancement of the remnant polarization in comparison with undoped BiFeO 3 thin films prepared by similar methods [141] (although saturated ferroelectric loops are never obtained in those cases), others support that remnant polarization falls off with niobium doping [142]. Apart from niobium, doping with Ti 4+ in the Fe 3+ positions is also a common method used to decrease the electrical conductivity in BiFeO 3 materials [61,62,121,122], although once again some works describe just the opposite effect [139]. In fact, there is not a generalized agreement regarding the charge compensation mechanisms; [61,122,143] in this context, it has been recently suggested that the charge compensation mechanism in Ti-doped BiFeO 3 ceramics may shift from an electronic compensation mechanism in the grain interior to a vacancy compensation mechanism in the grain boundary due to Ti 4+ segregation, this having a key role in the multiferroic properties [62].…”

“…As described in the literature the grain growth during sintering can be inhibited through the addition of dopants as La 3+ [108], Sm 3+ [116], Zn 2+ [65], Pb 2+ [117], Nb 5+ [63,118] or Ti 4+ [61,62]. Grain growth control by the effect of a third component is in fact very common in polycrystalline ceramics.…”

“…This charge can be compensated through reduction of Fe 3+ to Fe 2+ [114,120], annihilation of oxygen vacancies [121] or creation of Bi 3+ or Fe 3+ cationic vacancies [122]. These defects may also affect the grain growth [61,62].…”

“…Thus, it has been described in the literature that rare earth dopants like La 3+ [52,53], Gd 3+ [52,54], Nd 3+ [52], Sm 3+ [52,55], Y 3+ [56], or Ho 3+ [57] may have the desired effect of stabilizing the BiFeO 3 phase and decreasing the amount of secondary phases when replacing some Bi 3+ cations in the A positions of the perovskite structure. However, these dopants may diminish the electric polarizability of the A positions [52,58,59], so alternatively the use of transition ions like Mn 3+ [60] or Ti 4+ [61][62][63] for substituting the Fe 3+ cations in B positions, has been recently proposed. Nevertheless, the addition of a third component must be taken cautiously since in many cases they can have the contrary effect stabilizing one of the secondary phases (or both of them) [63][64][65][66], with an analogous result to that described by Valant et al [43].…”

“…Apart from niobium, doping with Ti 4+ in the Fe 3+ positions is also a common method used to decrease the electrical conductivity in BiFeO 3 materials [61,62,121,122], although once again some works describe just the opposite effect [139]. In fact, there is not a generalized agreement regarding the charge compensation mechanisms; [61,122,143] in this context, it has been recently suggested that the charge compensation mechanism in Ti-doped BiFeO 3 ceramics may shift from an electronic compensation mechanism in the grain interior to a vacancy compensation mechanism in the grain boundary due to Ti 4+ segregation, this having a key role in the multiferroic properties [62]. Finally, Zr 4+ [144], V 5+ [145] or W 6+ [146] are other donor-like dopants which have been used to improve the ferroelectric properties of BiFeO 3 materials.…”