The origin of pyroelectricity in tourmaline at varying temperature

Although tourmaline is a common pyroelectric material, the origins of pyroelectricity in tourmaline at varying temperature are still unclear. In the present work, based on the crystallographic data obtained from X-ray diffraction refinement, we calculated the intrinsic electric dipole moments of the typical coordination polyhedra ([XO9], [YO6], [ZO(6)], [TO4], [BO3]) in tourmaline unit cell along c-axis at various temperature ranging from 25 degrees C to 300 degrees C. The theoretical pyroelectric coefficients obtained based on these intrinsic electric dipole moments were consistent with the experimental results, indicating that the pyroelectric coefficient of tourmaline at varying temperature is mainly originated from the intrinsic electric dipole moment changes of the [XO9], [YO6], [ZO(6)], [TO4], [BO3] polyhedra along c-axis. Furthermore, the deformations of the [SiO4] tetrahedra and [BO3] polyhedra along c-axis direction were dominant in the change of total intrinsic electric dipole moment in the tourmaline unit cell. These results were further supported by the analyses of the polarized Raman spectra and infrared spectra. (c) 2018 Elsevier B.V. All rights reserved.