title: A new β-CdTeO3polymorph with a structure related to α-CdTeO3.
abstract: A new β-CdTeO3polymorph was obtained by hydrothermal synthesis and its structure was solved ab initio from powder X-ray diffraction data. It appears that the structure of β-CdTeO3(Pnma, Z = 16, a = 7.45850(3) Å, b = 14.52185(6) Å, c = 11.04584(5) Å) is closely related to that of α-CdTeO3(P21/c, Z = 8, a = 7.790(1) Å, b = 11.253(2) Å, c = 7.418(1) Å, β = 113.5(1)°) previously reported. The 3D framework of β-CdTeO3is built of both [CdO6] distorted octahedra and [CdO7] mono-capped trigonal prisms and three different tellurium polyhedra: trigonal pyramids [TeIVO3E] and trigonal bipyramids [TeIVO4E] and [TeIVO3+1E] (E denotes the lone pair of TeIV). The electronic structure calculations based on density functional theory methods show that at the ground state α-CdTeO3is slightly more stable than β-CdTeO3with an energy difference of 4.64 kJ mol-1. The band structures confirm the results of optical UV-Vis spectroscopy measurements: both polymorphs are wide bandgap semiconductors with Eg= 3.55 eV for β-CdTeO3and Eg= 3.91 eV for α-CdTeO3. The DOS calculations for both polymorphs enable one to understand that the presence of the [TeIVO4E] polyhedra in β-CdTeO3(absent in α-CdTeO3) lowers its bandgap. Above 540 °C β-CdTeO3transforms into α-CdTeO3in a first order phase transition.
authors.affiliation: Laboratoire CRISMAT, UMR 6508 CNRS ENCAEN, 6 bd Maréchal Juin, 14050 CAEN Cedex 4, France. nicolas.barrier@ensicaen.fr.
authors.forename: Morgane
authors.initials: M
authors.lastname: Poupon
authors.affiliation: Laboratoire CRISMAT, UMR 6508 CNRS ENCAEN, 6 bd Maréchal Juin, 14050 CAEN Cedex 4, France. nicolas.barrier@ensicaen.fr.
authors.forename: Nicolas
authors.identifier: http://orcid.org/0000-0002-5184-2246
authors.initials: N
authors.lastname: Barrier
authors.affiliation: Laboratoire CRISMAT, UMR 6508 CNRS ENCAEN, 6 bd Maréchal Juin, 14050 CAEN Cedex 4, France. nicolas.barrier@ensicaen.fr.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Petit
authors.affiliation: Laboratoire CRISMAT, UMR 6508 CNRS ENCAEN, 6 bd Maréchal Juin, 14050 CAEN Cedex 4, France. nicolas.barrier@ensicaen.fr.
authors.forename: Sophie
authors.initials: S
authors.lastname: Boudin