Stress induced effects on piezoelectric polycrystalline potassium sodium niobate thin films

resumo

The piezoelectric market is ruled by lead-based compounds that should be substituted by environmentally friendly materials. Despite the substantial literature on lead-free candidates available, stress effects on the dielectric, piezoelectric and ferroelectric performance of thin films from the nano- to macroscale have been barely addressed until now. In this work, a combination of multiscale characterization techniques is used to disclose the induced mechanical deformation impact on the dielectric, polar and structural properties of polycrystalline lead-free potassium sodium niobate (KNN) thin films fabricated on platinized silicon (Pt/Si(100)), strontium titanate (Pt/STO(100)) and magnesium oxide (Pt/MgO(100)) substrates. A tensile residual stress state characterizes KNN films on Pt/Si (+210 +/- 28 MPa), while KNN films on Pt/STO and Pt/MgO (-411 +/- 18 MPa and -494 +/- 26 MPa, respectively) evidence a compressive residual stress condition. Films with the highest compressive state (on Pt/MgO) exhibit the lowest dielectric losses with the highest electric permittivity and the maximum electric polarization; concomitantly they present the most dense and homogeneous microstructure, with small grains and a narrow grain size distribution. In contrast, tensile residual stress films (on Pt/Si) show the smallest polarization with an almost negligible out-of-plane component of piezoresponse. Of relevance, phase transition temperatures are markedly affected by the type and magnitude of the residual stress: they are the lowest for KNN films on Pt/MgO and highest for KNN films on Pt/Si. The narrowest temperature range for tetragonal phase is recorded for KNN films on Pt/MgO. For the first time, an approach to generate a morphotropic phase boundary in KNN thin films by use of compressive residual stress is thus demonstrated. This work highlights the impact of stress, as a key parameter in the performance of KNN polycrystalline thin films. These results have implications in terms of understanding lead-free ferroelectric/piezoelectric behaviour and its application/commercialization.

palavras-chave

K0.5NA0.5NBO3 CERAMICS; ELECTRICAL-PROPERTIES; RAMAN-SCATTERING; DEPOSITION

categoria

Materials Science; Physics

autores

Pinho, R; Vilarinho, R; Moreira, JA; Zorro, F; Ferreira, P; Ivanov, M; Tkach, A; Costa, ME; Vilarinho, PM

Grupos

G2 - Materiais Fotónicos, Eletrónicos e Magnéticos

Projectos

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

Desenvolvimento de materiais sustentáveis para aplicações em dispositivos para electrónica flexível e geração de energia (FLEXIDEVICE)

Electric-Field Engineered Lattice Distortions (E-FiELD) for optoelectronic devices (E-FiELD)

agradecimentos

This work was developed within the scope of the project CICECO - Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020; FLEXIDEVICE project PTDC/CTMCTM/29671/2017, and through IDMEC, under LAETA, UIDB/50022/2020, financed by national funds through the FCT/MEC (PIDDAC). Rui Vilarinho and J. Agostinho Moreira acknowledge FCT for financial support, under the projects PTDC/NAN-MAT/0098/2020, UIDB/04968/2021 and UIDP/04968/2021. Rui Pinho, Fatima Zorro and Alexander Tkach acknowledge FCT for financial support, under the studentships SFRH/BD/12069/2016, 2021.05950.BD, and individual FCT grant 2021.02284.CEECIND, respectively.