Potential of energy harvesting in barium titanate based laminates from room temperature to cryogenic/high temperatures: Measurements and linking phase field and finite element simulations

This paper studies the energy harvesting characteristics of piezoelectric laminates consisting of barium titanate (BaTiO₃) and copper (Cu) from room temperature to cryogenic/high temperatures both experimentally and numerically. First, the output voltages of the piezoelectric BaTiO₃/Cu laminates were measured from room temperature to a cryogenic temperature (77 K). The output power was evaluated for various values of load resistance. The results showed that the maximum output power density is approximately 2240 nW cm^-3. The output voltages of the BaTiO₃/Cu laminates were also measured from room temperature to a higher temperature (333 K). To discuss the output voltages of the BaTiO₃/Cu laminates due to temperature changes, phase field and finite element simulations were combined. A phase field model for grain growth was used to generate grain structures. The phase field model was then employed for BaTiO₃ polycrystals, coupled with the time-dependent Ginzburg-Landau theory and the oxygen vacancies diffusion, to calculate the temperature-dependent piezoelectric coefficient and permittivity. Using these properties, the output voltages of the BaTiO₃/Cu laminates from room temperature to both 77 K and 333 K were analyzed by three dimensional finite element methods, and the results are presented for several grain sizes and oxygen vacancy densities. It was found that electricity in the BaTiO₃ ceramic layer is generated not only through the piezoelectric effect caused by a thermally induced bending stress but also by the temperature dependence of the BaTiO₃ piezoelectric coefficient and permittivity.