Structural and luminescent studies of erbium‐doped CaZrO₃ green‐emitting nanophosphors

Abstract

Erbium (Er) (0.5, 1.0 and 1.5 wt%)-doped CaZrO nanophosphors were synthesized by the sol-gel method using poly(vinyl alcohol) as the chelating agent. Their structural and photoluminescence properties were studied using X-ray diffraction (XRD), field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS), transmission electron microscopy (TEM), photoluminescence and Fourier transform infrared spectroscopy (FTIR). The XRD patterns of the samples confirm that nanoscale crystallite sizes. Agglomeration of the samples was observed using field emission scanning electron microscopy images. Energy dispersive spectroscopy measurements confirmed the existence of Ca, Zr, O and Er in the samples. Average particle sizes for the samples were calculated from transmission electron microscopy images. FTIR spectra clearly show characteristic absorption bands related to the metal oxides, as well as some other organic molecules. The photoluminescence spectra show bands in the green region. The Commission International de l'Eclairage coordinates were calculated and found to be in green region.

New near‐infrared emissions and energy transfer in Er3+‐doped MgAl layered double hydroxides

“…Porosnicu has claimed that an extremely weak emission at 840 nm had been detected in the Er 3+ ‐doped CeO 2 , and the emission was assigned to the 2 H 11/2 → 4 I 13/2 transition of Er 3+ . [ 58 ] The present samples were excited with 565 nm (2.20 eV), and the ground state electrons could not jump to the 2 H 11/2 (2.34–2.30 eV) level (seen in Figure 9). So the present emission at 850 nm may be due to the 4 S 3/2 → 4 I 13/2 but not to the 2 H 11/2 → 4 I 13/2 transition.…”

“…In general, downconversion emissions for Er 3+ produce green ( 2 H 11/2 → 4 I 15/2 , 4 S 3/2 → 4 I 15/2 ) and red emissions ( 4 F 9/2 → 4 I 15/2 , 4 I 9/2 → 4 I 15/2 ), and the green emissions were often stronger than the red emissions. [ 38,57–62,64 ] Here, all Er‐MgAl‐LDH‐ n ( n = 1, 2, 3, 4) exhibited strong infrared emissions at 720, 780, and 850 nm under 480, 520, and 565 nm excitations, respectively, along with red emission at 650 nm under 220 nm excitation (seen in Figure 6II and Figure 7). Strong emissions at 720, 780, and 850 nm have been seldom reported in previous downconverted emission spectra for Er 3+ ‐doped materials.…”

“…The emission at ~650 nm is often found in the downconversion emission spectra of Er 3+ ‐doped compounds [ 30,31,34,55,57 ] as well as the upconversion emission spectra of RE/Er 3+ co‐doped compounds. [ 33,35,58–64 ] When samples were excited with 480, 520, and 565 nm wavelengths, some strong emissions at 720, 780, and 850 nm, respectively, occurred, but the emission at 650 nm did not emerge. The possible reason is that the energy at 480, 520, and 565 nm wavelengths was too low to produce a 650 nm emission.…”

“…To understanding the origins of strong emissions at 720, 780, and 850 nm, the energy transfer diagram of Er 3+ doped into MgAl‐LDH‐ n ( n = 1, 2, 3, 4) is described (seen in Figure 9 and based on relevant references [ 30–35,38,42,55,58–61,67 ] and the relationship between the wavelength and energy is as follows: Electrons at ground state level ( 4 I 15/2 ) can absorb energy and jump to all high energy levels and convert to excited state electrons, while Er 3+ ‐doped Mg n Al‐LDH‐n ( n = 1, 2, 3, 4) were excited by the 220 nm wavelength (5.64 eV). When the excited state electrons come back to the ground state, some excited state electrons may release energy by nonradiative transition, and some excited state electrons at 4 F 9/2 energy level may release energy by radiative transition, resulting in the 650 nm emission.…”