Enhanced Electromechanical Response and Thermal Stability of 0.93(Na_1/2Bi_1/2)TiO₃‐0.07BaTiO₃ Through Aerosol Deposition of Base Metal Electrodes

Abstract

Na1/2Bi1/2TiO3‐based relaxor ferroelectrics are extensively investigated for use in transduction applications because of their relatively large electromechanical properties. Integration of these materials into devices, however, requires better temperature stability in addition to electromechanical properties. This work demonstrates a novel approach to enhance the temperature stability of the long‐range ferroelectric order as well as to enhance electromechanical properties in a non‐ergodic relaxor 0.93(Na1/2Bi1/2)TiO3‐0.07BaTiO3 (NBT‐7BT) without changing the chemical composition through, for example, chemical substitutions or second phase particles. The approach involves the room temperature deposition of copper electrodes directly on the relaxor ceramic substrate using the aerosol deposition (AD) method. The collision of solid‐state particles with the substrate surface during AD results in large impact and residual stresses, inherent to the AD process, which are shown with piezo‐response force microscopy to induce long‐range ferroelectric domain ordering in non‐ergodic relaxor NBT‐7BT. Using Raman spectroscopy, the magnitude and depth profile of the stress‐induced transformation are determined. It is demonstrated that deposition‐induced stresses significantly increase the temperature stability of the electromechanical properties, where long‐range ferroelectric ordering is observed up to 150 °C, which is approximately 41 °C higher than NBT‐7BT samples without the AD processed electrode. Moreover, the AD treatment also facilitates ferroelectric domain switching at a lower electric field, enabling maximum polarization at a relatively lower field and an enhancement in the piezoelectric response. It is shown that the deposition‐induced stress is responsible for such an enhancement. Importantly, this impact‐stress‐driven tailoring of electromechanical properties can potentially be utilized for other functional ceramic materials as well, where internal residual stress can result in enhanced functional properties.

Composite Scheme for Deferred Thermal Depolarization of Lead-Free Bi0.5Na0.5TiO3-Based Piezoelectric Ceramics

“…For the BNT−7BT substrate using the aerosol deposition of an electrode, the deposition-induced residual stresses result in long-range ferroelectric domain ordering. 49 These results reveal that the evolution of the domain structure is supposed to be caused by the increased R phase and residual stresses.…”

“…The increase in ⟨ξ⟩ means that the incorporation of Ag significantly increases the local polar ordering and mean size of the domain structure. Larger domain sizes and enhanced ferroelectric ordering usually favor delayed thermal depolarization behavior . Note that there is a strong dependence between the domain and phase structure. ,− For example, complex domains of about 100 nm were observed in the BNT–4BT ceramics with the R phase, while the BNT–6BT (MPB) ceramics consisted mainly of nanometer-sized domains. , Meanwhile, the domain pattern of BNT-based materials is also affected by the stresses.…”

“…Note that there is a strong dependence between the domain and phase structure. ,− For example, complex domains of about 100 nm were observed in the BNT–4BT ceramics with the R phase, while the BNT–6BT (MPB) ceramics consisted mainly of nanometer-sized domains. , Meanwhile, the domain pattern of BNT-based materials is also affected by the stresses. For the BNT–7BT substrate using the aerosol deposition of an electrode, the deposition-induced residual stresses result in long-range ferroelectric domain ordering . These results reveal that the evolution of the domain structure is supposed to be caused by the increased R phase and residual stresses.…”

“…Larger domain sizes and enhanced ferroelectric ordering usually favor delayed thermal depolarization behavior. 49 Note that there is a strong dependence between the domain and phase structure. 48,50−52 For example, complex domains of about 100 nm were observed in the BNT−4BT ceramics with the R phase, while the BNT−6BT (MPB) ceramics consisted mainly of nanometer-sized domains.…”

Investigating the Feasibility of Preparing Metal–Ceramic Multi-Layered Composites Using Only the Aerosol-Deposition Technique

“…The development of metal films by AD is still in its early stages. Thus far, AD has been used to deposit metal films such as Cu [16,17], Ag [15,18], Fe [19,20] and Fe-based amorphous alloys [21]. In this study, we have deposited metal layers of Al, which has not yet been reported.…”