Nanosecond fluctuation kinetics of luminescence hopping quenching originated from the 5d1\mathrm{5d^{1}} level in the Ce3+:YPO4⋅0.8H2O\mathrm{Ce^{3+}:YPO_{4}·0.8H_{2}O} nanocrystals

We study the nanosecond energy transfer kinetics detected at dipole allowed 5d1–4f1 transition and originated from the lowest 2Γ1 level of the Ce3+ ions doped into the rhabdophane-type YPO4·0.8H2O nanocrystals synthesized by microwave hydrothermal treatment. We show that the luminescence quenching in the nanocrystals is determined by two processes depending on Ce3+ (energy donor) concentration at constant OH− (energy acceptors) concentration. At 0.2 mol% Ce3+ the luminescence quenching is mainly determined by direct (static) quenching caused by vibrations of OH− groups. At 2.0 mol% Ce3+ the quenching accelerates due to energy migration from the Ce3+ ions with poor acceptor surrounding to the Ce3+ ions with the nearby OH− acceptors. In the latter case we observe fluctuation kinetics of the luminescence impurity hopping quenching starting immediately after static ordered stage of the decay kinetics. We obtain that for dipole allowed the 5d–4f transition in the Ce3+ donor the CDD microparameter of the Ce3+–Ce3+ energy migration and CDA microparameter of Ce3+–OH− energy transfer are in strong correlation with the higher spontaneous emission rate for dipole allowed transition in Ce3+ comparing to dipole forbidden transition in Nd3+

Vacuum ultraviolet spectroscopic analysis of Ce3+Ce^3+-doped hexagonal YPO4⋅0.8H2OYPO_4·0.8H_2O based on exchange charge model

The hexagonal YPO4·0.8H2O:Ce3+ nanophosphors are successfully prepared by the microwave–hydrothermal technique for the first time. The 4f–5d excitation spectrum of Ce3+ ion in the synthesized samples is recorded at 10 K using synchrotron radiation after the crystalline phase structure was confirmed by the X-ray diffraction(XRD) analysis. The combination of the effective Hamiltonian model for 5d1 configuration of Ce3+ ions and the exchange charge model of crystal-field (CF) theory is employed to analyze both the present electronic spectra measured by us and the case of the tetragonal crystalline powder sample of YPO4:Ce3+ reported by van Pieterson et al. (Phys. Rev. B: Condens. Matter. 65 (2002) 045113). The calculated 5d electronic energy levels of Ce3+ ions doped in two crystalline phases are in good agreement with the experimental results. The obtained CF strength parameters for both the cases suggest that Ce3+ ions in the hexagonal phase experience a stronger CF effect. In addition, the expansion technique of CF Hamiltonian along the chosen point-group chain is proposed to qualitatively understand the relationship between the local structure around Ce3+ impurities and the observed 5d energy splitting pattern for two cases