  Single phase barium titanate-bismuth ferrite ((1-x)BaTi$_3$-(x)BiFe$_3$,
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 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.
