Incommensurately Modulated Crystal Structure and Photoluminescence Properties of Eu2O3- and P2O5-Doped Ca2SiO4 Phosphor

Hiromi Nakano; Shota Ando; Konatsu Kamimoto; Yuya Hiramatsu; Yuichi Michiue; Naoto Hirosaki; Koichiro Fukuda

doi:10.3390/ma13010058

Incommensurately Modulated Crystal Structure and Photoluminescence Properties of Eu₂O₃- and P₂O₅-Doped Ca₂SiO₄ Phosphor

Materials (Basel). 2019 Dec 20;13(1):58. doi: 10.3390/ma13010058.

Authors

Hiromi Nakano^{1

2}, Shota Ando², Konatsu Kamimoto², Yuya Hiramatsu³, Yuichi Michiue⁴, Naoto Hirosaki⁴, Koichiro Fukuda³

Affiliations

¹ Cooperative Research Facility Center, Toyohashi University of Technology, Toyohashi 441-8580, Japan.
² Department of Applied Chemistry and Life Science, Toyohashi University of Technology, Toyohashi 441-8580, Japan.
³ Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya 466-8555, Japan.
⁴ National Institute for Materials Science, Tsukuba 305-0044, Japan.

Abstract

We prepared four types of Eu₂O₃- and P₂O₅-doped Ca₂SiO₄ phosphors with different phase compositions but identical chemical composition, the chemical formula of which was (Ca_1.950Eu³⁺_0.013☐_0.037)(Si_0.940P_0.060)O₄ (☐ denotes vacancies in Ca sites). One of the phosphors was composed exclusively of the incommensurate (IC) phase with superspace group Pnma(0β0)00s and basic unit-cell dimensions of a = 0.68004(2) nm, b = 0.54481(2) nm, and c = 0.93956(3) nm (Z = 4). The crystal structure was made up of four types of β-Ca₂SiO₄-related layers with an interlayer. The incommensurate modulation with wavelength of 4.110 × b was induced by the long-range stacking order of these layers. When increasing the relative amount of the IC-phase with respect to the coexisting β-phase, the red light emission intensity, under excitation at 394 nm, steadily decreased to reach the minimum, at which the specimen was composed exclusively of the IC-phase. The coordination environments of Eu³⁺ ion in the crystal structures of β- and IC-phases might be closely related to the photoluminescence intensities of the phosphors.

Keywords: dicalcium silicate; incommensurate structures; optical materials; phase compositions; phase transitions.