Effects of thermal anneal temperature on electrical properties and energy-storage density of Bi(Ni1/2Ti1/2)O3–PbTiO3 thin films

Ferroelectric thin films in Bi(Ni1/2Ti1/2)O3–PbTiO3 system are promising materials for applications in high energy-storage embedded capacitors and piezoelectric micro-devices due to their good dielectric and piezoelectric properties. However, the electrical properties of the films are largely dependent on the synthesis conditions. In this work, Bi(Ni1/2Ti1/2)O3–PbTiO3 films near the MPB composition were prepared via chemical solution deposition and the effects of thermal anneal temperatures on the microstructure and electrical properties were investigated. XRD patterns showed that the films annealed under 750 °C have a pure perovskite phase, while a small amount of pyrochlore phase was detected above 800 °C. AES depth-composition analysis revealed that Bi and Pb evaporated very severely as annealing temperature increased above 800 °C, which is responsible for the appearance of pyrochlore phase and pin-pores in the films. Furthermore, current–voltage measurement confirmed that the changes in morphology and the volatilization of Bi/Pb at high temperature which caused non-stoichiometry may be responsible for the changes in leakage-current density. Dielectric and ferroelectric properties of the films are also quite dependent on the annealing temperature. As a result, the as-prepared film annealed at 750 °C shows the largest permittivity and polarization with a giant energy-storage density of 46.7 J/cm3 and the optimal piezoelectric response with a local effective piezoelectric coefficient d33⁎ of 62.2 pm/V.