Exploring oxygen pressure effects on phase transitions, ferroelectric properties, and ultrasonic transducer performance in (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 thin films by pulsed laser deposition

This study investigates the effect of oxygen pressure (P O 2 ) during pulsed laser deposition on the structural, ferroelectric, and piezoelectric properties of thin films. Films were deposited at P O 2 levels of 8.6, 10, 11.5, and 12.7 Pa. The optimal ferroelectric properties were observed at 10 Pa, with a remnant polarization of 2.97 μ C/cm 2 , a coercive field of 33.80 kV/cm, and a saturation polarization of 11.88 μ C/cm 2 , closely matching the target composition. X-ray diffraction and Raman spectroscopy confirmed the presence of a morphotropic phase boundary (MPB) near room temperature. The MPB shifts toward lower temperatures with increasing P O 2 , as characterized by the photoacoustic technique. Frequency measurements based on photoacoustic and piezoelectric effects demonstrated promising performance for piezoelectric micromachined ultrasonic transducers, with resonance frequencies ranging from 9.5 to 13 MHz.