Polarization arising from a disorder

Polarization, i.e., spontaneous surface charge, is usually associated with the 10, polar, out of 32 existing crystallographic classes. Usually, disorder is associated with the decreasing of the polarization, like in the case of ferroelectric to paraelectric phase transition. However, a polarization can also arise from an anisotropic disorder by the displacement of polar entities from their random / symmetry-related positions, i.e., polar disorder. In this presentation, I show three examples of system with a polar disorder: (I) polar amorphous thin films[1], in which thermal strass gradients align the polar TiO₆ bonding untints[2-5]; (II) polar disorder in centrosymmetric amino acid crystals develops as a result of solvent incorporation[6], e.g., water[7-8]; (III) molecular mixed crystals[9-11]. I also present new results that show a connection between the pyroelectric effect and the polar disorder in molecular mixed crystals.

References:

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[4] D. Ehre, et al., in Flexoelectricity in Solids: From Theory to Applications (Eds.: A. K. Tagantsev, P. V. Yudin), World Scientific Publishing Co Pte Ltd, 2015.

[5] V. Shelukhin, et al., Adv Funct Mater 2011, http://dx.doi.org/10.1002/adfm.201001613.

[6] E. Meirzadeh, et al., Angew Chem Int Edit 2018, http://dx.doi.org/10.1002/anie.201800741.

[7] S. Piperno, et al., Angew Chem Int Edit 2013, http://dx.doi.org/10.1002/anie.201301836.

[8] E. Meirzadeh, et al., J Am Chem Soc 2016, http://dx.doi.org/10.1021/jacs.6b09190.

[9] E. Meirzadeh, et al., Nat Commun 2016, http://dx.doi.org/10.1038/Ncomms13351.

[10] E. Meirzadeh, et al., Accounts Chem Res 2018, http://dx.doi.org/10.1021/acs.accounts.8b00054.

[11] S. Dishon Ben Ami, et al., http://dx.doi.org/https://doi.org/10.1002/anie.202213955.