Control of ferroelectric phase transition in nano particulate NBT–BT based ceramics

Lead free relaxor NBT–BT based ceramic compositions were prepared using sol–gel method. The samples were sintered around 1140 °C for 3–4 h in the air. The characterization was done using X-ray diffraction (XRD), filed emission scanning electron microscope (FESEM), energy dispersive spectrometry (EDS), Raman, Fourier transform infrared (FTIR), dielectric and P–E loop measurements. The XRD patterns recorded at room temperature confirmed the phase formation of the samples. From FESEM micrographs, the particle sizes were estimated for calcined powders and are found to be in the range of 50–70 nm. The analysis of both Raman and FTIR spectral data of the samples also indicated the distortion of NBT lattice with the addition of Ba2+ and Nd3+ ions. It was found that the dielectric and piezoelectric properties of NBT–BT compositions beyond the morphotrophic phase boundary (MPB) are rather sensitive to the presence of tetragonal phase in addition to the rhombohedral phase. NBT ceramics exhibit a decrease in diffusive factor with increasing BT content, implying a degradation of relaxor feature leading to the normal ferroelectric nature. The ceramic samples employed in the present study exhibited variation in P–E hysteresis loops.

Modified Curie–Weiss law fitting of BT1, NBT1, NBT2 and NBT3 samples and inset shows modified Curie–Weiss law fitting for NBT at 10 kHz frequency.Figure optionsDownload as PowerPoint slideHighlights
► For the first time we have studied the effect of Nd3+ and BT on structural changes in NBT lattice.
► Ti metal powder was used instead of TiO2 to synthesize the ceramics using sol–gel.
► FTIR and Raman spectra were recorded for NBT–BT based ceramics.
► In dielectric measurements the transition from relaxor to normal with doping is observed.