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

Abstract

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. SEM studies 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 0.6 wt.% of SrTiO3 showed the best ferroelectric and piezoelectric response with maximum value of Pr (8.24 µC/cm2), minimum value of Ec (5.73 kV/mm) and maximum d33 value (∼46 pC/N).

Keywords

• (Bi0.5Na0.5)0.94Ba0.06TiO3
• morphotropic phase boundary
• complex permittivity
• AC conductivity
• activation energy