Structural and optical characterization of Er-doped CaMoO₄down-converting phosphors

Abstract

xEr2O3–(1−x)CaMoO4 (x = 1, 3, 5, 7 and 10 mol%) nanoparticles were synthesized by solid-state sintering at 800°C. X-ray diffraction studies confirmed the tetragonal crystal structure of CaMoO4, while the doped samples show the co-existence of cubic Er2O3 and tetragonal CaMoO4 and rule out the replacement of Ca2+ by Er3+ in the structure. The crystal unit-cell dimensions, phase concentration and atomic position coordinates were determined by Rietveld refinement. The short-range structure of CaMoO4 consists of tetrahedral MoO4 and snub disphenoid deltahedral CaO8 units, while the unit cell of Er2O3 consists of two types of ErO6 octahedral units. All MoO4 units contain Mo—O bonds of equal lengths, whereas two types of slightly different Ca—O bond lengths exist in CaO8. Raman spectra of the doped samples show only Mo—O vibrational modes and the Raman peaks of Er2O3 are masked by Mo—O bond vibrations. CaMoO4 shows bluish-green emission at 500 nm, while Er-doped samples show strong green emission under UV excitation. UV irradiation (380 nm) induces down-conversion green emission at 531 nm and 552 nm and good color purity in 1 mol% Er2O3–CaMoO4 sample which makes it a potential candidate for applications in optical devices.

Opto-mechano-thermo-sensitive allochroic luminescence based on coupled dual activators in tantalate towards multidimensional stimulus sensing

“…Furthermore, it is known that Er 3+ ions also possess excellent up-conversion performance induced by NIR irradiation besides the aforesaid down-conversion emission. 13,31 We further investigated the up-conversion emission capacity of LiTaO 3 :Bi 3+ /Er 3+ upon 980 nm laser irradiation. The emission spectra only displayed sharp peaks of Er 3+ emitters without broad-band emission of Bi 3+ , but the emission intensity improved significantly compared with the LiTaO 3 :Er 3+ sample (Fig.…”

“…27–29 As for activators, Er 3+ ions have two dominant radiative transitions, 2 H 11/2 / 4 S 3/2 → 4 I 15/2 (green) and 4 F 9/2 → 4 I 15/2 (red), and can produce multi-mode emissions in different colors via excitation wavelength fine-selectivity, such as down-conversion and up-conversion photoluminescence (DC and UC PL). 30,31 Furthermore, based on the fluorescence intensity ratio (FIR) technique, the temperature can also be measured from the emission intensity ratio of thermally coupled levels of Er 3+ ( 2 H11/2/ 4 S3/2) in a noncontact and noninvasive method. 32,33…”

“…[27][28][29] As for activators, Er 3+ ions have two dominant radiative transitions, 2 H 11/2 / 4 S 3/2 → 4 I 15/2 (green) and 4 F 9/2 → 4 I 15/2 (red), and can produce multi-mode emissions in different colors via excitation wavelength fine-selectivity, such as down-conversion and up-conversion photoluminescence (DC and UC PL). 30,31 Furthermore, based on the fluorescence intensity ratio (FIR) technique, the temperature can also be measured from the emission intensity ratio of thermally coupled levels of Er 3+ ( 2 H11/2/ 4 S3/2) in a noncontact and noninvasive method. 32,33 However, according to previous reports, only semi-conductive piezo-crystals (SrZnOS, CaZnOS) have effectively realized the opto-mechano-thermo-responsive luminescence of Er 3+ in a single host, while the chemical stability and environmental toxicity of oxysulfide prevent their practicability.…”

Synthesis and Characterization of Luminescent Er3+-Doped Natural Fluorapatite

“…2, some Er 3+ ions were substituted to the Ca(II) site as an activator for emission when excited under UV. Figures 4a and 4b exhibit two excitation bands at 279 nm & 274 nm (maximum) and 353 nm & 343 nm, which correspond to the different transitions of Er 3+ − O 2− charge transfer state 47,48 and 4 I 15/2 → 4 G 7/2 , [16][17][18] respectively. PL emission spectra of both two samples also have similar records in the visible range.…”

“…Utilizing the shielding effect of the 4f shell in Er-ions, a narrow emission band with a temperature invariant wavelength can be obtained up to room temperature. [16][17][18] Many apatite compounds have been used as the host material for phosphors for their remarkable and excellent physical and chemical stability. 19,20 It is also known that Fions in fluorapatite increase thermal stability compared to hydroxyapatite.…”