Synthesis and Characterization of Ca1- x Eu x ZrO3 as Environmentally Friendly Inorganic Yellow Pigments

Kohei Minagawa; Yuichi Nishiguchi; Ryohei Oka; Toshiyuki Masui

doi:10.1021/acsomega.0c05959

Synthesis and Characterization of Ca_{1- x} Eu _x ZrO₃ as Environmentally Friendly Inorganic Yellow Pigments

ACS Omega. 2021 Jan 22;6(4):3411-3417. doi: 10.1021/acsomega.0c05959. eCollection 2021 Feb 2.

Authors

Kohei Minagawa¹, Yuichi Nishiguchi¹, Ryohei Oka², Toshiyuki Masui^{3

4}

Affiliations

¹ Department of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101, Koyama-cho Minami, Tottori 680-8552, Japan.
² Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101, Koyama-cho Minami, Tottori 680-8552, Japan.
³ Faculty of Engineering, Tottori University, 4-101, Koyama-cho Minami, Tottori 680-8552, Japan.
⁴ Center for Research on Green Sustainable Chemistry, Tottori University, 4-101, Koyama-cho Minami, Tottori 680-8552, Japan.

Abstract

Eu²⁺-doped calcium zirconates, Ca_1-x Eu _x ZrO₃ (0 ≤ x ≤ 1), were synthesized as novel environmentally friendly inorganic yellow pigments by the conventional solid-state reaction method. The crystal structure, morphology, optical properties, and color were characterized. The Eu²⁺-doped samples strongly absorbed blue light in the wavelength range of 435-480 nm, which was caused by the 4f-5d allowed transition of Eu²⁺. The color of the sample gradually became brilliant yellow with increasing the Eu²⁺ content. Among the samples synthesized in this study, the brightest yellow color was obtained with the Ca_0.7Eu_0.3ZrO₃ (a* = +11.5 and b* = +70.7) sample. Compared with the commercially available praseodymium yellow pigment (a* = -3.28, b* = +70.3), the yellowness value (b*) of Ca_0.7Eu_0.3ZrO₃ was comparable and the redness value (a*) was higher. As a result, this pigment exhibited a reddish yellow color as compared with praseodymium yellow. In addition, this pigment was chemically stable. Therefore, the Ca_0.7Eu_0.3ZrO₃ pigment has the potential to become a novel environmentally friendly inorganic yellow pigment.