Tourmalines pyroelectric effect depending on the chemical composition and cation oxidation state

[Marco E. Ciriotti]

Referenza:
▪ Chernyshova, I.A., Vereshchagin, O.S., Malyshkina, O.V., Goncharov, A.G., Kasatkin, I.A., Murashko, M.N., Zolotarev, A.A., Frank-Kamenetskaya, O.V. (2021): Tourmalines pyroelectric effect depending on the chemical composition and cation oxidation state. Journal of Solid State Chemistry, 303, 122512.

Abstract:
Tourmaline (the first natural pyroelectric material discovered) is the most common borosilicate on Earth characterized by a great variety of ionic substitutions at all structural sites. In this work the mosaicity and chemical inhomogeneity of single crystal samples of natural Fe-Mg and synthetic Ni- and Cu-rich tourmalines were characterized by X-ray diffraction (rocking curves,  – 2θ scanning) and energy-dispersive X-ray spectroscopy. The iron oxidation state (Fe3+/Fe) in natural tourmalines was determined by Mӧssbauer spectroscopy. The pyroelectric properties of tourmalines were examined at room temperature by the dynamic pyroelectric measurement method. This approach allowed estimating the primary pyroelectric coefficient with the error smaller than ± 0.15 μCm-2K-1. Based on the original and published data, it was shown that one of the main factors determining the pyroelectric properties of tourmaline is the ion oxidation state. It was found that the values of the Na-tourmaline pyroelectric coefficient were inversely proportional to the amount of divalent cations (Mg, Fe) and / or directly proportional to the amount of Al3+. This can be used for the directed synthesis of tourmalines with the required pyroelectric properties.