Enhanced Energy Conversion and Storage Properties of Sn-Doped BaTiO3 Bulk Ceramics Using Compressive Stresses

The effect of uniaxial compressive stress on the pyroelectric, energy storage and harvesting properties in BaTi1−xSnxO3 (x = 0, 0.08, 0.09) bulk ceramics is investigated. The energy storage density varies from 0.058 J/cm3 to 0.076 J/cm3 (increase in temperature, 25–55°C) at 5 MPa and 0.058–0.113 J/cm3 (increase in stress, 5–160 MPa) at 25°C for BT-9Sn (BaTi0.91Sn0.09O3). The results show that stress confinement can increase the stored energy density by 94% and efficiency by 20% at 25°C in BaTi0.91Sn0.09O3. The stress-biased pyroelectric coefficient (p) was found to be maximum for BT (BaTiO3) at room temperature. The thermal/mechanical energy harvesting is estimated using the Olsen cycle (at various stress/temperature biases) and hybrid (thermomechanical) cycle. The maximum thermal and mechanical energy conversion are found as 102 kJ/m3 (25–70°C and 0.5–3 kV/mm at a contact stress of 5 MPa) and 134 kJ/m3 (5–160 MPa and 0.25–2 kV/mm at 25°C) for BT-8Sn (BaTi0.92Sn0.08O3) and BT, respectively. The mechanical energy conversion cycle is beneficial compared to the thermal (Olsen) cycle because of increased energy conversion density and easy implementation. The hybrid cycle shows an improved energy harvesting potential of 171 kJ/m3 when operated between 25°C (5 MPa) and 127°C (160 MPa) at 0.25–2 kV/mm for BaTiO3.