Revealing multiphase coexistence of R-O-T phases in BaTiO3-CaTiO3-BaSnO3 electroceramics for energy harvesting and storage response with piezo actuation

The (Ba_1-xCa_x)(Sn_yTi_1-y)O₃ piezoelectric ceramics (where x=0.016, y=0.024; x=0.032, y=0.048; x=0.048, y=0.072; x=0.064, y=0.096; x=0.08, y=0.12) were designed by conventional solid state reaction method. The crystal structure for the composition of x=0.064 and y=0.096 (abbreviated as BCST-4) possesses the coexistence of non-centrosymmetric rhombohedral-orthorhombic-tetragonal (R-O-T) tri-lattice symmetries at room temperature, as demonstrated by the structural Rietveld refinement, Raman analysis, and temperature dependence of dielectric study. Because of the R-O-T multiphase coexistence, BCST-4 possesses a superior electromechanical and piezoelectric property viz. k_p ∼ 0.45, strain ∼ 0.100 %, d₃₃* ∼ 649 pm/V, and an improved d₃₃ ∼ 452 pC/N, which is comparable to commercially available soft PZT ceramics (d₃₃ ⁓ 370 pC/N). For BCST-4 ceramics, an exceptional electrostriction coefficient Q₃₃ ∼ 0.0434 m⁴/C² value was attained. The intrinsic piezo-actuation DC strain was observed to be 130 microstrain (με) and 188 με with ε₃₃ and ε₃₁ modes respectively. The BCST-4 ceramic exhibits a maximum output power of 1.03 mW, a power density of 13.5 µW/mm³, a maximum output current of 88 µA, and an open circuit voltage V_pp of 28 V which successfully glowed ‘SPPU’ panel having 40 red commercial light-emitting diodes (LEDs). The energy storage study reveals that BCST-4 ceramics exhibit a maximum energy storage density (W_rec) of 165.87 mJ/cm³ with efficiency (ƞ) 68.00 %. Therefore, the improvement in electrostriction coefficient, piezoelectric charge coefficient, and energy storage response indicates that BCST-4 ceramic has the potential for actuator, energy harvesting, and energy storage applications.