Quantitative Determination of the Effective Mn4+ Concentration in a Li2TiO3:Mn4+ Phosphor and Its Effect on the Photoluminescence Efficiency of Deep Red Emission

Takuya Hasegawa, Yoshinori Nishiwaki, Fumito Fujishiro, Shinnosuke Kamei, Tadaharu Ueda

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Obtaining highly efficient photoluminescence with Mn4+-activated phosphors, which have been extensively studied in diverse lighting devices, requires the precise control of the manganese valence states. However, this control is difficult to achieve because manganese ions can have various valence states ranging from divalent to heptavalent. Additionally, the concentrations of Mn ions in each valence state, especially the effective Mn4+ concentration, have never been quantitatively determined in a phosphor crystal lattice. The relationship between the effective Mn4+ concentration and the luminescence properties of Mn4+-activated phosphors is of current interest for improving the phosphor properties. In the present study, the effective Mn4+ concentration in Li2TiO3:Mn4+ (LTO:Mn) phosphors prepared by the sol-gel method with heating at various temperatures was quantitatively analyzed by X-ray absorption near-edge spectroscopy. Moreover, the effect of the existence of Mn2+, Mn3+, and Mn4+ ions on the photoluminescence efficiency was investigated. The effective Mn4+ concentration was found to be over 60% in all phosphor samples. The quantum efficiencies (QEs) of all LTO:Mn phosphors strongly depend on the effective Mn4+ concentration. In particular, the LTO:Mn phosphor prepared by heating at 800 °C (LTO:Mn@800) contained the highest effective Mn4+ concentration of 98.1% and exhibited the highest internal QE of 31.6%. The results of this work provide new and important insights for the development of Mn4+-activated phosphors with high efficiency.

Original languageEnglish
Pages (from-to)19856-19862
Number of pages7
JournalACS Omega
Volume4
Issue number22
DOIs
Publication statusPublished - 2019 Nov 26
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

Fingerprint Dive into the research topics of 'Quantitative Determination of the Effective Mn<sup>4+</sup> Concentration in a Li<sub>2</sub>TiO<sub>3</sub>:Mn<sup>4+</sup> Phosphor and Its Effect on the Photoluminescence Efficiency of Deep Red Emission'. Together they form a unique fingerprint.

Cite this