Surface piezoelectricity and pyroelectricity in centrosymmetric materials: A case of α-glycine

Surface pyroelectricity and piezoelectricity induced by water incorporation during growth in α-glycine were investigated. Using the periodic temperature change technique, we have determined the thickness (~280 µm) of the near surface layer (NSL) and its pyroelectric coefficient (160 pC/(K × cm2) at 23◦C) independently. The thickness of NSL remains nearly constant till 60◦C and the pyroelectric effect vanishes abruptly by 70◦C. The piezoelectric effect, 0.1 pm/V at 23◦C measured with an interferometer, followed the same temperature dependence as the pyroelectric effect. Abrupt disappearance of both effects at 70◦C is irreversible and suggests that water incorporation to α-glycine forms a well defined near surface phase, which is different form α-glycine because it is polar but it too close to α-glycine to be distinguished by X-ray diffraction (XRD). The secondary pyroelectric effect was found to be <14% of the total, which is unexpectedly small for a material with a large thermal expansion coefficient. This implies that water incorporation infers minimal distortions in the host lattice. This finding suggests a path for the control of the piezoelectric and pyroelectric effects of the crystals using stereospecific incorporation of the guest molecules. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.This work was supported by the collaborative program of the Israeli Ministry of Science with the Russian Foundation for Basic Research, grant № 3-16492. This research was made possible in part by RFBR (Grant No. 19-52-06004 MNTI_a), and the Government of the Russian Federation (Act 211, Agreement 02.A03.21.0006). The work has been supported in part by the Ministry of Science and Higher Education of the Russian Federation under Project № 3.9534.2017/8.9. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020 and UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. The equipment of the Ural Center for Shared Use “Modern Nanotechnology” UrFU was used. I.L. expresses his gratitude to Estate of Olga Klein–Astrachan fund, grant № 721977