Engineering the Microstructure and Functional Properties of 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ Thin Films

Abstract

Lead-free piezoelectric 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BZT−BCT) thin films deposited by chemical solution deposition on platinized silicon substrates using ethylene glycol and ethanol solvents for alkaline-earth carboxylates and transition-metal alkoxides, respectively, are studied. Undoped and manganese-doped BZT-BCT films prepared by repeated deposition of a 0.1 M precursor solution and multistep annealing at 850 °C until reaching the thickness of about 120 nm exhibit a predominantly columnar microstructure with preferential (111) orientation of the perovskite phase. The Mn-doped films' room-temperature permittivity is about 670 at 1 kHz, which is ≈30% higher than the permittivity of their undoped counterparts at the same frequency and temperature while maintaining a similar tan δ ≈ 0.02. Mn-doping effectively reduces the leakage of BZT-BCT films, contributing to a saturated ferroelectric hysteresis loop with a remnant polarization of 5 μC cm −2 and a coercive field of 80 kV cm −1 . The maximum polarization and recoverable energy storage density are about 32 μC cm −2 and 10 J cm −3 , respectively, with 69% efficiency at 1160 kV cm −1 . The energy-storage properties remain almost unaffected after 2 million cycles at a field of 800 kV cm −1 . The piezoelectric d 33 coefficient measured by double-beam laser interferometry is about 20 pm V −1, while the corrected value of d 33 ≈ 34 pm V −1 taking into account the ratio of the electrode size to substrate thickness being equal to unity.