Sr doped BNKT sensor materials for structural health monitoring

In the current paper lead-free piezoelectric ceramics BNKT, [Bi_0.5(Na_0.85K_0.15)_0.5]_1-xSr_xTiO₃ (where x=0, 0.02, 0.04, 0.06) are prepared by conventional solid state route. Calcination studies are carried out to optimize the properties. XRD studies are carried out to confirm the perovskite phase formation. The powders are prepared in the form of discs of 10 mm diameter and 1.0 mm thickness. Subsequently, compacted samples are sintered in the range of 1175 °C to 1200 °C to improve the density. The relative densities of all the samples are determined by first principle method. Poling dependence and stability of lead free BNKT ceramic system are investigated. The effect of Sr doping piezoelectric charge coefficient (d₃₃), and coupling coefficient (K_p) are discussed in detail. Dielectric properties are studied by varying strontium content. Partial doping of Sr on BNKT ceramic improved the piezoelectric and dielectric properties substantially. The electric measurements reveals that the ceramic with x=0.03 & 0.04 has the better piezoelectric and dielectric properties. The obtained properties are piezoelectric charge coefficient (d₃₃), 140 pC/N, dielectric constant (ε), 850 and dielectric loss (tan δ), 0.045. BNKT ceramic prototypes are designed to operate with lamb waves for the purpose of monitoring the structural integrity of structures.