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Issue 12, 2014
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The role of the Ca vacancy in the determination of the europium position in the energy gap, its valence state and spectroscopic properties in KCa(PO3)3

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Abstract

A new very promising red phosphor KCa1−xEux(PO3)3 (x = 1–5%) has been grown by the solid state method. Its luminescent quantum efficiency is close to 100% and the emission is stable over a wide temperature range i.e. 90% and 60% of the room temperature emission intensity remains at 200 °C and at 600 °C, respectively. The chromaticity coordinates were calculated as being x = 0.63, y = 0.37. The IR and Raman spectra were measured, and the maximum phonon energy of KCa1−xEux(PO3)3 is 1276 cm−1. In the measured emission and excitation spectra of all samples only Eu3+ ion emission was observed, emission of Eu2+ is not present. Quantum mechanical calculations showed that in a perfect crystal the 5d levels of Eu2+ are embedded in the conduction band. Consequently, neither absorption nor emission assigned to the Eu2+ ions could be observed. The presence of a calcium vacancy is crucial for the explanation of the observed spectrum. The existence of a Ca2+ vacancy compensates for the charge of Eu3+ and results in the creation of the magnetic moment which moves the 4f levels to the valence band. Thus, transitions to the Eu3+ excited levels located in the energy band gap are observed.

Graphical abstract: The role of the Ca vacancy in the determination of the europium position in the energy gap, its valence state and spectroscopic properties in KCa(PO3)3

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Publication details

The article was received on 19 Nov 2013, accepted on 27 Dec 2013 and first published on 07 Jan 2014


Article type: Paper
DOI: 10.1039/C3CP54875A
Citation: Phys. Chem. Chem. Phys., 2014,16, 5581-5588
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    The role of the Ca vacancy in the determination of the europium position in the energy gap, its valence state and spectroscopic properties in KCa(PO3)3

    A. Watras, A. Matraszek, P. Godlewska, I. Szczygieł, J. Wojtkiewicz, B. Brzostowski, G. Banach, J. Hanuza and P. J. Dereń, Phys. Chem. Chem. Phys., 2014, 16, 5581
    DOI: 10.1039/C3CP54875A

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