Nanoscale ferroelectricity in pseudo-cubic sol-gel derived barium titanate - bismuth ferrite (BaTiO3– BiFeO3) solid solutions

Abstract

Single phase barium titanate-bismuth ferrite ((1-x)BaTiO3-(x)BiFeO3, BTO-BFO) solid solutions were prepared using citric acid and ethylene glycol assisted sol-gel synthesis method. Depending on the dopant content the samples are characterized by tetragonal, tetragonal-pseudocubic, pseudocubic and rhombohedral structure as confirmed by Raman spectroscopy and XRD measurements. An increase of the BFO content leads to a reduction in the cell parameters accompanied by a decrease in polar distortion of the unit cell wherein an average particle size increases from 60 up to 350 nm. Non zero piezoresponse was observed in the compounds with pseudocubic structure while no polar distortion was detected in their crystal structure using X-ray diffraction method. The origin of the observed non-negligible piezoresponse was discussed assuming a coexistence of nanoscale polar and non-polar phases attributed to the solid solutions with high BFO content. A coexistence of the nanoscale regions having polar and non-polar 2 character is considered as a key factor to increase macroscopic piezoresponse in the related compounds due to increased mobility of the domain walls and phase boundaries.

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

“…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.…”

Crystal Structure and Concentration-Driven Phase Transitions in Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) Prepared by the Sol–Gel Method

“…Raman spectroscopy was employed to access the short-range structural details of the studied compounds. In addition, this technique sensitively probes the presence of defects and disorders [ 37 , 38 , 39 ]. Figure 4 a compares 532 nm excited Raman spectra of polycrystalline LuFeO 3 and ScFeO 3 samples sintered at 1100 °C.…”

Evolution of the crystal structure and magnetic properties of Sm-doped BiFeO3 ceramics across the phase boundary region

“…Diffraction studies afford important knowledge about the average crystal structure of studied compounds, while Raman spectroscopy provides molecular level information on short range structure or local symmetry which is difficult to acquire by other structuresensitive techniques [44]. In addition, Raman spectroscopy is very sensitive to the presence of defects and disorders [45][46][47]. Fig.…”