Evolution of crystal structure of Ba and Ti co-doped BiFeO3 ceramics at the morphotropic phase boundary

Peculiarities of the Crystal Structure Evolution of BiFeO3–BaTiO3 Ceramics across Structural Phase Transitions

“…Based on the obtained diffraction data, the results of DSC/DTA and PFM measurements performed for Bi 1−x Ba x Fe 1−x Ti x O 3 solid solutions, as well as our previous data (reported in [38]), the temperature-composition phase diagram was clarified (Figure 7). elongation of the unit cell and thus with polar distortion of the lattice mainly caused by off-center displacement of the Bi(Ba) ions.…”

“…It should be noted that the evolution of mixed structural state into single phase cubic structure is characterized by small enthalpy associated with the transition and conventional DSC measurements performed for the compounds could not reveal this structural transition, unlike the structural data detecting this phenomenon ( Figure 5). In contrast, the structural transition from the rhombohedral phase to the cubic phase observed in the compound with x = 0.15 can be easily detected by DSC measurements as well as the diffraction experiments [38]. The evolution of the mixed structural state into the single phase state confirms the intrinsic character of the phase separation observed for the compounds with 0.2 ≤ x ≤ 0.35, which is associated with high chemical homogeneity of the compounds.…”

“…The available data describing the evolution of the crystal structure in the system Bi 1−x Ba x Fe 1−x Ti x O 3 as well as the physical parameters declared in the different studies [37,[40][41][42][43] have an ambiguous character and should be clarified. Our recent temperature-dependent structural measurements [38] performed for the compounds having dominant a rhombohedral phase within the mentioned phase boundary have revealed unexpected strengthening of the rhombohedral distortions at elevated temperatures. The most recent structural data obtained by the authors point to the non-monotonous character of the phase evolution from the polar rhombohedral to the cubic-like phase assuming a reinforcement of polar type distortion, which also affects piezoresponse in the compounds.…”

“…The compounds in vicinity of the rhombohedral-pseudocubic phase boundary are characterized by increased piezoelectric coefficient d 33 , reaching maximum value of about 250 pm/V in the compounds with 33% of BaTiO 3 content. It should be noted that structural state of the solid solution with one-third of BaTiO 3 content is characterized by the dominant pseudocubic phase with minor (~35%) fraction of the rhombohedral phase [37][38][39]. Moreover, our recent investigation involving the piezoresponse force microscopy measurements has revealed a polarizable state in compounds with x~0.33, 0.35, while according to the XRD data, these compounds possess single phase cubic structure [37].…”

“…Simultaneous doping at the A-and B-positions of the perovskite lattice allows to modify the sub-lattices responsible for polar and magnetic orders [35][36][37]. Thus, in compounds Bi 1−x Ba x Fe 1−x Ti x O 3 , an increase of the dopant content leads to structural transition from the polar rhombohedral phase to the polar tetragonal phase through the formation of an intermediate (pseudo)-cubic structure [8,[37][38][39]. The compounds in vicinity of the rhombohedral-pseudocubic phase boundary are characterized by increased piezoelectric coefficient d 33 , reaching maximum value of about 250 pm/V in the compounds with 33% of BaTiO 3 content.…”