Influence of temperature on the structural and color properties of nickel molybdates. (February 2020)

• Record Type: Journal Article
• Authors: da Silva, Maíra V.; de Oliveira, Daynara F.M.; Oliveira, Henrique S.; Siqueira, Kisla P.F.
• Is Part Of: Materials research bulletin. Volume 122(2020)
• Publication Date: 2020-02
• Subjects: A. Ceramics -- B. Chemical synthesis -- C. X-ray diffraction -- D. Color centers -- D. Crystal structure; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2019.110665
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: The heat treatment resulted in nickel molybdates with varying colors and crystalline structures, which showed good performance for pigmentation of the clear epoxy resin. Highlights: NiMoO4 ceramic materials were prepared by a co-precipitation method. The materials presented various yellow-green shades. Heat treatment influenced the colorimetric parameters. NiMoO4 showed good performance for pigmentation of clear epoxy resin. Abstract: In this work, nickel molybdates were synthesized by co-precipitation method, at 70 °C, and were thermally treated at temperatures ranging from 300 to 1000 °C. Firstly, the hydrated precursor (NiMoO4 .0.65H2 O) was obtained, followed by calcination at 300–600 °C to produce a mixture of β- and α-NiMoO4 phases. The pure α phase could only be obtained above 700 °C. The relationships among the crystal structure, colorimetric parameters, and spectroscopic properties (Raman and UV–vis diffuse reflectance) of the NiMoO4 were investigated. Although the thermochromic β phase was not obtained in the pure form, the heat treatments enabled tuning of the band gaps of the materials, with the color changing from yellow to greenish-yellow and the band gap changing from 3.23 to 2.33 eV. The colorimetric parameters (L*a*b*) were determined and the coloring performances of the NiMoO4 materials were evaluated by incorporating them into a clear polymer substrate material.