Crystal Structure Change with Applied Electric Field for (100)/(001)-oriented Polycrystalline Lead Zirconate Titanate Films

ACS Appl. Mater. Interfaces

Hasegawa

Ishihama

et al. 2021

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Strong electromechanical coupling is observed in tetragonal Pb-free 0.7(Bi 0.5 Na 0.5 )-TiO 3 -0.3BaTiO 3 films, which is far from the morphotropic phase boundary, prepared by pulsed laser deposition on a Si substrate. The tensile strain induced during cooling causes in-plane polarization in an oriented film on a Si substrate, while an epitaxial film grown on a SrTiO 3 substrate exhibits out-ofplane polarization. S−E curve analysis reveals that the obtained piezoelectric coefficient for the film on the Si substrate (d 33,f ≈ 275 pm/V) is approximately eight times higher than that for the epitaxial film on the SrTiO 3 substrate (d 33,f ≈ 34 pm/V). In situ X-ray diffraction analysis confirms the occurrence of domain switching under an electric field from in-plane to out-of-plane polarization. An effective piezoelectric stress coefficient, e 31,eff , of ∼19 C/m 2 is obtained from a Si cantilever sample, which is the highest among the reported values for Pb-free piezoelectric films and is comparable to those for Pb-based films. The significant piezoelectric response produced by domain switching in the Pb-free materials with the composition far from the morphotropic phase boundary will expand future applications due to their both outstanding properties and environmental sustainability.

Section: Resultsmentioning

confidence: 89%

Section: Methodsmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Large Piezoelectric Response in Lead-Free (Bi_0.5Na_0.5)TiO₃-Based Perovskite Thin Films by Ferroelastic Domain Switching: Beyond the Morphotropic Phase Boundary Paradigm

ACS Appl. Mater. Interfaces

Hasegawa

Ishihama

et al. 2021

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Large Electromechanical Responses Driven by Electrically Induced Dense Ferroelastic Domains: Beyond Morphotropic Phase Boundaries

Nakajima

ACS Appl. Electron. Mater.

Nakaki

et al. 2020

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Piezoelectric materials based on ferroelectrics with a perovskite structure are among the most useful materials because they can convert electrical energy into mechanical energy and vice versa. Although piezoelectricity strongly depends on ferroelastic domain density, there are no general methods to controllably fabricate dense domain structures in ferroelectric films. Here, we report a mechanism to achieve a large piezoresponse based on an electrically induced dense ferroelastic domain structure in ferroelectric films. We demonstrate a large piezoelectric coefficient of 310 pm/V under both bipolar and unipolar electric fields, which is about 3 times larger than that in epitaxial single-crystalline thin films of tetragonal PbZr 0.4 Ti 0.6 O 3 grown on silicon substrates. Analysis by a combination of in situ Raman and piezoresponse force microscopy suggests that the large piezoelectric response can be explained by the motion of dense ferroelastic domain walls. This mechanism provides a general method to enhance the piezoelectric properties of ferroelectric materials.

Large irreversible non-180° domain switching after poling treatment in Pb(Zr, Ti)O3 films

Yasui

Oikawa

Applied Physics Letters

et al. 2016

(111¯)/(111)-oriented rhombohedral Pb(Zr0.65Ti0.35)O3 films with different domain fractions were epitaxially grown on various single crystals. The volume fraction of (111)-polar-axis oriented domains in as-deposited films, Vpol.(as-depo.), was controlled by selecting a single crystal substrate with a different thermal expansion coefficient. Applying an electric field, referred to as “poling treatment”, resulted in irreversible non-180° domain switching from the (111¯)-oriented domain (non-polar-axis) to the (111)-oriented domain (polar-axis), which was observed by synchrotron X-ray diffraction. Remanent polarization (Pr) values were higher than those estimated using the proportional relationship with Vpol.(as-depo.). However, the experimental Pr values were in good agreement with the values estimated using the volume fraction of (111)-oriented domains after applying the poling treatment. In rhombohedral Pb(Zr0.65Ti0.35)O3 films, 30%−50% of the (111¯)-oriented domains switched irreversibly to (111)-oriented domains as a result of the poling treatment. The present results show that the domain structures of films may change dramatically after the poling process, and both before and after the poling state should be characterized in order to interpret polarization and piezoelectric behaviors. This study helps to clarify the ferroelectric and piezoelectric properties of Pb(Zr, Ti)O3 films after poling treatment.