PZT/PZT and PZT/BiT Composite Piezo-Sensors in Aerospace SHM Applications: Photochemical Metal Organic + Infiltration Deposition and Characterization

Abstract

The composition of fine-ground lead zirconate-titanate powder Pb(Zr0.52Ti0.48)O3, suspended in PZT and bismuth titanate (BiT) solutions, is deposited on the curved surface of IN718 and IN738 nickel-based supper alloy substrates up to 100 µm thickness. Photochemical metal organic and infiltration techniques are implemented to produce smooth, semi-dense, and crack-free random orientated thick piezoelectric films as piezo-sensors, free of any dopants or thickening polymers. Every single layer of the deposited films is heated at 200 °C with 10 wt.% excess PbO, irradiated by ultraviolet lamp (365 nm, 6 watt) for 10 min, pyrolyzed at 400 °C, and subsequently annealed at 700 °C for one hour. This process is repeated successively until reaching the desired thickness. Au and Pt thin films are deposited as the bottom and top electrodes using evaporation and sputtering methods, respectively. PZT/PZT and PZT/BiT composite films are then characterized and compared to similar PZT and BiT thick films deposited on the similar substrates. The effect of the composition and deposition process is also investigated on the crystalline phase development and microstructure morphology as well as the dielectric, ferroelectric, and piezoelectric properties of piezo-films. The maximum remnant polarization of Pr = 22.37 ± 0.01, 30.01 ± 0.01 µC/cm2, the permittivity of εr = 298 ± 3, 566 ± 5, and piezoelectric charge coefficient of d33 = 126, 148 m/V were measured versus the minimum coercive field of Ec = 50, 20 kV/cm for the PZT/PZT and PZT/BiT thick films, respectively. The thick film piezo-sensors are developed to be potentially used at frequency bandwidth of 1–5 MHz for rotary structural health monitoring and also in other industrial or medical applications as a transceiver.

Temperature Effects on Electromechanical Response of Deposited Piezoelectric Sensors Used in Structural Health Monitoring of Aerospace Structures

“…The procedure of piezo-film deposition on the curved surface of the blades was similar to what was described in [31,34]. The samples went through gold bottom electrode deposition (600 nm per layer), prior to fabrication of thick film piezo-sensors.…”

“…The resultant composite piezoelectric thick films were deposited on the curved surface of the blades up to 100 mm of thickness using sol–gel technique and were polarized as explained in [36]. All the samples were dried at 200 °C for 5 min, pyrolyzed at 400 °C for 5 min, UV irradiated and annealed at 600–700 °C in a tube furnace under atmosphere pressure for 30 or 60 min with a heating rate of 5 °C/min [31,34].…”

“…In this composition, the PZT element guarantees the high piezoelectric properties, while the BiT ( T c = 550 °C) ensures high temperature performance of the sensors. Preliminary characterization of deposited piezo-films was also performed as reported in [31,32,34] to ensure the accurate structural composition and surface morphology, as well as mechanical, dielectric, ferroelectric and piezoelectric properties of the piezo-sensors.…”

“…These challenges together with the shear lag, which occurs due to the adhesive layer, and detachment uncertainties of stacked sensors at high temperatures/high speeds, led us to replace PWAS by deposition of piezo-ceramic thick films on curved metallic substrates using sol-gel photochemical metal-organic method. For the past decade, the authors have been focused on the development of different integrated thin and composite thick piezoelectric films and characterizations [30,31,32,33,34,35], polarization process [36], and application of such films in the SHM of aerospace structures at ambient temperature and different rotary speeds [37]. This study, on the other hand, represents the effects of temperature variations on E/M impedance signatures of sol-gel derived deposited piezoelectric thick films deployed in SHM of aerospace structures.…”

Damage Identification in Structural Health Monitoring: A Brief Review from its Implementation to the Use of Data-Driven Applications

“…In some cases, the actuators are located as close as possible to the sensors so that a transducer can serve as both an actuator and a sensor. This type of duality is exemplified by piezoelectric arrays [80].…”