Effects of Sr2+ doping on the electrical properties of (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics

The influence of SrTiO3 addition on the microstructure and various electrical properties of (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNTBT6) ceramics, fabricated by a conventional high temperature solid state reaction, was investigated. Analysis of X-ray diffraction patterns revealed the formation of phase pure materials with tetragonal unit cell structure, tetragonality parameter c/a in the interval from 0.9940 to 1.0063 and crystallite sizes ranging from 33-76 nm for addition of 0.2 to 1 wt.%of SrTiO3. SEMstudies indicated that Sr2+ doping led to decrease in grain size and non-homogeneity of grain distribution for higher SrTiO3 amount (>0.6 wt.%). Complex impedance, modulus, and conductivity studies indicated the presence of grains and grain boundary contribution, non-Debye type of relaxation and NTCR behaviour of the test ceramic samples. Temperature dependent real part of complex permittivity showed peaks at 475?C and the dielectric loss tangent showed peaks corresponding to 125?C and 475?C for almost all compositions. AC activation energies, computed using Arrhenius relation in the temperature range of 325-500?C for the BNTBT6 ceramic compositions having SrTiO3 concentration from 0.2 to 1.0 wt.%, were seen to have maximal values at the lowest measurement frequency. Amongst the different chosen doped BNTBT6 ceramic compositions, the composition having 0.6wt.%of SrTiO3 showed the best ferroelectric and piezoelectric response with maximum value of Pr (8.24 ?C/cm2), minimum value of Ec (5.73 kV/mm) and maximum d33 value (?46 pC/N).