Role of Synthesis Method on Luminescence Properties of Europium(II, III) Ions in β-Ca 2 SiO 4: Probing Local Site and Structure
- State Key Laboratory of Crystal Materials
- Shandong University
- ShanghaiTech University
- Bhabha Atomic Research Centre
The europium ion probes the symmetry disorder in the crystal structure, although the distortion due to charge compensation in the case of aliovalent dopant remains interesting, especially preparation involves low and high temperatures. This work studies the preparation of the β-Ca 2 SiO 4 (from here on C 2 S) particle from Pechini (C 2 SP) and hydrothermal (C 2 SH) methods, and its luminescence variance upon doping with Eu 2+ and Eu 3+ ions. The blue shift of the charge-transfer band (CTB) in the excitation spectra indicates a larger Eu 3+ -O 2- distance in Eu 3+ doped C 2 SH. The changes in vibrational frequencies due to stretching and bending vibrations in the FTIR and the Raman spectra and binding energy shift in the XPS analysis confirmed the distorted SiO 4 4- tetrahedra in C 2 SH. The high hydrothermal temperature and pressure produce distortion, which leads to symmetry lowering although doping of aliovalent ion may slightly change the position of the Ca atoms. The increasing asymmetry ratio value from C 2 SP to C 2 SH clearly indicates that the europium ion stabilized in a more distorted geometry. It is also supported by Judd-Ofelt analysis. The concentration quenching and site-occupancy of Eu 3+ ions in two nonequivalent sites of C 2 S were discussed. The charge state and concentration of europium ions in C 2 SP and C 2 SH were determined using X-ray photoelectron spectroscopy measurements. The C 2 S particles were studied by X-ray powder diffraction, FTIR, Raman, BET surface area, TGA/DTA, electron microscopy, XPS, and luminescence spectroscopy. The impact of citrate ion on the morphology and particle size of C 2 SH has been hypothesized on the basis of the microscopy images. This study provides insights that are needed for further understanding the structure of C 2 S and thereby improves the applications in optical and biomedical areas and cement hydration.
|Tila||Julkaistu - 5 helmikuuta 2018|
|OKM-julkaisutyyppi||A1 Julkaistu artikkeli, soviteltu|