Surface Piezoelectricity and Pyroelectricity in Centrosymmetric Materials: A Case of α-Glycine

Abstract

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.

Glycine: The Gift that Keeps on Giving

“…One such "anomaly" is the surface piezoelectricity and pyroelectricity. [283,284] The bulk structure of α-glycine that crystallizes in the P2 1 /n space symmetry group is incompatible with pyro-or piezo-electric properties. Yet, these effects have been measured for crystals of this polymorph.…”

Surface Pyroelectricity and Piezoelectricity of Centrosymmetric Crystals

“…From the value of j 0 (Eq. ( 8)) we have deduced the total pyroelectric coefficient, a s , which is fairly large for a nonferroelectric material, � 1.6 × 10 À 10 C/(cm 2 • K) [9] at room temperature. [4] Figure 3.…”

“…( 7) (Figure 5a [9] ). At room temperature, the best fit was achieved for d = 288 � 25 μm (Figure 5b [9] ).Presence of such thick polar layers can be attributed to coalescence of clusters present in the supersaturated solution during the growth of the crystal. Such process is different than the classical crystal growth mechanism which considers sequential addition of single molecules or dimers.…”

2D Layered Dipeptide Crystals for Piezoelectric Applications

“…[ 28 ] It is even more surprising because the first 2D ferroelectricity (the effect closely related to piezoelectricity) has been demonstrated in thin films of organic polymer polyvinylidene fluoride (PVDF). [ 12 ] Since then, piezoelectricity in organic 2D piezoelectrics has been studied mostly theoretically and experimentally in self‐assembled monolayers [ 29 ] and on the surface of amino acid crystals [ 30 ] and nucleobases. [ 31 ]…”