Black Current: Structure, Characterization, and Optoelectronic Properties of Ce3 Cl3 [MoO6 ]

Katharina V Dorn; Björn Blaschkowski; Heiko Bamberger; Joris van Slageren; Klaus Doll; Ralf Claus; Yosuke Matsumoto; Hidenori Takagi; Ingo Hartenbach

doi:10.1002/chem.201901038

Black Current: Structure, Characterization, and Optoelectronic Properties of Ce₃ Cl₃ [MoO₆ ]

Chemistry. 2019 Jun 12;25(33):7921-7926. doi: 10.1002/chem.201901038. Epub 2019 May 14.

Authors

Katharina V Dorn^{1

2}, Björn Blaschkowski¹, Heiko Bamberger³, Joris van Slageren³, Klaus Doll⁴, Ralf Claus⁵, Yosuke Matsumoto⁵, Hidenori Takagi⁵, Ingo Hartenbach¹

Affiliations

¹ Institute of Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
² Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius Väg 16 C, 10691, Stockholm, Sweden.
³ Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
⁴ Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
⁵ Max-Planck-Institute for Solid-State Research, Heisenbergstrasse 1, 70569, Stuttgart, Germany.

PMID: 30972829
DOI: 10.1002/chem.201901038

Abstract

The admixture of CeO₂ , Ce, CeCl₃ , and MoO₃ with an excess of LiCl as flux in evacuated silica ampules leads to large black single crystals as well as a black microcrystalline powder of Ce₃ Cl₃ [MoO₆ ] after tempering at 850 °C for three days. The title compound crystallizes in the hexagonal space group P6₃ /m (a=934.93(4), c=538.86(2) pm) with two formula units per unit cell. The crystal structure consists of rather unusual trigonal-prismatic [MoO₆ ]^6- units besides Ce³⁺ ions in a tetra-capped trigonal-prismatic coordination, formed by four Cl^- and six O^2- ions. The black color is related to an optical band gap of 1.35(2) eV, which was determined by diffuse reflectance spectroscopy and confirmed by theoretical calculations. The low band gap between the 4f¹ state of cerium (HOMO) and the 5d⁰ state of molybdenum (LUMO) gave rise to the idea of electronic excitation between these two states by IR irradiation, creating a drop in the resistivity of the material, which was detected by appropriate measurements.

Keywords: EPR spectroscopy; cerium; density functional calculations; optoelectronic properties; oxidomolybdates.