SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 6: Perovskite and photovoltaics I (joint session HL/CPP)

CPP 6.8: Talk

Monday, March 27, 2023, 11:45–12:00, JAN 0027

Spontaneous Polarization in NaNbO₃ — •Kisung Kang¹, Saud Bin Anooz², Jutta Schwarzkopf², Matthias Scheffler¹, and Christian Carbogno¹ — ¹The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft and IRIS-Adlershof of the Humboldt-Universität zu Berlin — ²Leibniz-Institut fur Kristallzüchtung (IKZ)

The perovskite NaNbO₃ is regarded as a promising lead-free piezoelectric material, also because its polarization properties can be further tailored via strain engineering. [1] In thin films, lattice strain can be incorporated by the heteroepitaxial growth on lattice mismatch. By tuning the epitaxial strain in the films, different polymorphs with distinctively different polarization strength and orientation can be realized [2, 3]. We investigate this question by using density-functional theory at the semi-local level of theory, which we carefully validate with hybrid-functional calculations. By this means, we compute the spontaneous polarization for ten phases of NaNbO₃ as a function of stress and strain. In line with experiments, we confirm that the monoclinic Pm phase features a non-vanishing in-plane polarization, the orientation of which is independent of the strain. Conversely, the polarization direction of the orthorhombic Pmc2₁ phase depends on the applied tensile strain. We analyze the underlying electronic and atomistic mechanism and discuss how the relevant properties are influenced by phase transformations.

[1] N. Bein, et al., Phys. Rev. Mater. 6, 084404 (2022).

[2] J. Schwarzkopf, et al., J. Appl. Cryst. 45, 1015 (2012).

[3] S. B. Anooz, et al., Appl. Phys. Lett. 120, 202901 (2022).