Dielectric, Ferroelectric and Piezoelectric study of BNT-BT solid solutions around the MPB region

Peculiar Properties of Phase Transitions in Na0.5Bi0.5TiO3-xBaTiO3 (0<x<6) Lead-free Relaxor Ferroelectrics Seen Via Acoustic Emission

“…The ɛ' (T) curves exhibit two groups of smeared (diffused) humps and maxima: the low temperature humps corresponds to T lm , in the range of 150-200ºC and the high temperature maxima corresponds to T m in the range of 300-350ºC. These results are in good agreement with previous studies 10,19,21,[27][28][29][30][31]33 . For pure NBT the form of the ɛ' curve is not symmetric around T m : from the low temperature side it is steeper in comparison with the high temperature side, as observed previously 21 .…”

“…Previously the dielectric constant, measured on heating in NBT-6BT crystals, clearly shows the low temperature "hump" of ɛ' 19,[27][28][29][30] between of 140 and 220°C, accompanied by AE bursts between of 127 and 225°C, which also exhibits the bursts corresponding to T m ≈ 290°C and T p ≈ 390°C, respectively 33 . Recently, using the AE, it was confirmed that the temperature of this "hump", ascribed as the T lm , exhibits the strong frequency dispersion, whereas the T d exhibits no dispersion, and all these characteristic temperatures of NBT-6BT: T d ≈ 123°C, T lm ≈ 150÷180°C, T RE ≈ 225°C, T m ≈ 300÷310°C and T p ≈ 327°C have been successfully detected by AE 10 , in good agreement with the early detected data 33 .…”

“…When incorporating the Ba ions in A-site of NBT-xBT the dielectric anomalies smear and shift by the temperature, but the direction of such the shifts is not clearly seen due to smearing of dielectric curves as well as contradictory sometimes, especially concerning the T m [19][20][21][27][28][29] . Moreover, in pure NBT the maximum of ɛ' there is a clearly seen to be not symmetric: jump of ɛ' on some tens of degrees below T m , shifting to lower temperatures and gradually vanishing as the content of Ba increases 20,21 .…”

Evaluation of covalency of ions in lead-free perovskite-type dielectric oxides

“…The existing experimental results told us some difficulties in the fabrication by solid-state sintering because of vaporization of Bi, Na 2 O, K 2 O out of the materials, of which problem seemed settled in present, 21,24 and showed the boundaries and the effects for both systems. [21][22][23][24][25] Our results may be related to the boundaries in some chemical sense, and be utilized for the further chemical modification, which will eventually guide us to obtaining excellent lead-free actuators and energy harvesters.…”

“…The suggested system has already studied experimentally. [21][22][23] The studies focused on investigating morphotropy among the cubic, rhombohedral, tetragonal crystal structures, and also on finding any morphotropic effect on the properties. The similar studies were also done on the similar system Ba(BiK)TiO 3 , 24,25 contained K + instead of Na + , and focused on that among the three structures.…”