Effect of bismuth titanate on the properties of potassium sodium niobate-based ceramics

The effect of modifying the properties of KNN-based ceramics with Bi2Ti2O7 (BiT) been investigated in this work. The density measurements show that additions of BiT to the samples slightly increase the density values. Scanning electron microscope images of the samples indicate that the average sizes of the grains decrease with BiT addition while the volume of pores increase. X-ray diffraction results show that for (K0.5Na0.5)NbO3 based samples, a transformation from orthorhombic to pseudo-cubic phase is observed. For both K0.48Na0.48Li0.04)(Nb0.9Ta0.1)O3 and K0.48Na0.48Li0.04)(Nb0.86Ta0.1Sb0.04)O3-based compositions, the phase transition is from an orthorhombic-tetragonal coexistence to a tetragonal structure dominated phase coexistence. The dielectric constant, dielectric loss and resistivity values of the samples increase slightly with BiT addition. Good hysteresis curves are obtained in (K0.5Na0.5)NbO3-based samples only at low BiT amounts. Remnant polarization values between 9 μC/cm2 and 25 μC/cm2 are obtained for K0.48Na0.48Li0.04)(Nb0.9Ta0.1)O3 and K0.48Na0.48Li0.04)(Nb0.86Ta0.1Sb0.04)O3-based samples. With the exception of KNNLT samples where the d*33 values increase from 203 ± 7 pm/V at 0 mol% to 275 ± 6 pm/V at 0.35 mol%, the d*33 values of the samples gradually decrease with increasing BiT content. This work shows that to obtain good properties for KNN-based ceramics, only very small amounts of BiT are required