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In this work, we have investigated the near-infrared (NIR) photoluminescence, upconversion (UC), and long-lasting phosphorescence properties of Nd3+/Yb3+-doped Ca2SnO4 phosphors. Two-photon NIR qua...

Near-infrared (NIR) quantum cutting (QC) from the Tm3+: 1G4 state essentially occurs via a three-step cascade radiation (case 1) and two-step cross-relaxations (case 2) by varying the Tm3+ content (x) from 0.0005 to 0.05 in La2–xTmxBaZnO5. In case 1, with the Tm3+ content x < 0.005, the energy of the 1G4 excited state is down-converted to three NIR photons emitted at approximately 1200, 1480, and 1800 nm, with 3H4 and 3F4 acting as intermediate levels, while in case 2, with the Tm3+ content x ≥ 0.005, the energy will be triply cut into approximately 1800 nm photon emissions. The three-photon NIR QC phenomena are investigated in terms of the static and dynamic photoluminescence. Based on the dependence of cross-relaxation and concentration quenching on Tm3+ density, a rate-equation model was built to describe the energy transfer (ET) dynamics of Tm3+. The calculation of internal quantum yield (QY) was developed by considering nonradiative processes, and the maximum QY for photon emission at 1800 nm was 198...

The BaCaBO3F wide band gap host and the charge-compensated phosphors BaCaBO3F:Ln3+ (Ln = Ce, Tb, Gd) and BaCaBO3F:Ce3+,Tb3+ have been synthesized by a solid-state reaction method at high temperature. Their spectroscopic properties in the vacuum ultraviolet (VUV)–vis range have been investigated. The band gap of the host lattice is estimated at 7.8 eV, which is considerably higher than the value found from its diffuse reflectance spectrum. The 5d crystal field level locations, Stokes shift, and Huang–Rhys factor have been determined from the VUV excitation and near-UV emission spectra of BaCaBO3F:Ce3+. The 5d1 decay lifetime is 29 ns at x ∼ 0.005. Concentration quenching occurs for Ba1–2xCexNaxCaBO3F with maximum intensity at x ∼ 0.035 and with critical distance Rc = 17.7 A. An unusual broad, intense band in the excitation spectrum of BaCaBO3F:Gd3+ is assigned to a near-defect exciton. Very weak emission from 5D3, and intense green emission from 5D4, has been assigned for BaCaBO3F:Tb3+. In the VUV region, ...

A series of samples with nominal chemical formulas La 2-x Ce x CaB 10 O 19 and La 2 Ca 1-2x Ce x Na x B 10 O 19 were prepared by a solid state reaction route at high temperature. Their luminescence properties were investigated by the steady state excitation and emission spectra in the VUV-vis range, the luminescence decays, and the time-resolved emission spectra (TRES). The results demonstrate that Ce 3+ ions occupy two lattice sites in all samples. The lowest 5d absorption bands for two sites are at about 272 (La 3+ site) and 312 nm (Ca 2+ site), respectively. The emission for Ce 3+ in the La 3+ site shows a shorter decay time of 12 ns, and the doublet emission bands have maxima at about 291 and 310 nm. The emission for the Ce 3+ in Ca 2+ site has a longer lifetime of 26 ns with band maxima at about 329 and 355 nm. Efficient energy transfer between both sites occurs in the samples.