ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

The relationship between crystal structures and thermochromism in CoMoO₄

Rosiane K. S. Costa, Stéfani C. Teles, and Kisla P. F. Siqueira

Laboratory of Ceramic Materials and Raman Spectroscopy, Department of Chemistry, Federal University of Ouro Preto, Ouro Preto, Brazil

E-mail: kisla@ufop.edu.br

Received: 26 May 2020  Accepted: 20 July 2020

Abstract:

Abstract

The visible thermochromism of crystalline CoMoO₄ was investigated in a temperature range from 300 to 1000 °C. The microcrystals were obtained by the coprecipitation method followed by calcination. Through spectroscopic techniques, it was possible to monitor the phase transition from samples in the β-phase to α-phase, which is associated with the color change of the material from purple (β) to green (α). The phase transition was irreversible and proceeded approximately at 550 °C. Both polymorphs belong to C2/m (#12) space group and crystallize in the monoclinic arrangement. The colorimetric parameters allowed to follow the color differences obtained in the material according to the applied temperature. The relationship between crystal structure, colorimetric parameters, and spectroscopic properties was described in detail and help the understood of the thermochromic behavior in cobalt molybdate. The increase in the temperature allowed the band-gap tuning from 2.8 to 1.5 eV due to the change of color from purple to green, confirming the promising potential of these materials for use as temperature indicators that can be observed by the naked eye.

Graphic abstract

Keywords: Crystal structure; Characterization; Inorganic compounds; Thermochromic materials

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01294-z

Chemical Papers 75 (1) 237–248 (2021)