Low-Temperature Solid-State Synthesis and Upconversion Luminescence Properties in (Na/Li)Bi(MoO₄)₂:Yb³⁺,Er³⁺ and Color Tuning in (Na/Li)Bi(MoO₄)₂:Yb³⁺,Ho³⁺,Ce³⁺ Phosphors

Abstract

In this Article, we reported the synthesis and the upconversion luminescence (UCL) properties of a series of novel (Na/Li)­Bi­(MoO4)2:Yb3+,Er3+ [(N/L)­BMO:Yb3+,Er3+] and (Na/Li)­Bi­(MoO4)2:Yb3+,Ho3+,Ce3+ [(N/L)­BMO:Yb3+,Ho3+,Ce3+] phosphors. X-ray diffraction patterns and Rietveld refinements for several representative samples indicated the pure phase of as-prepared samples. The Yb3+,Er3+ codoped (N/L)­BMO presented bright green luminescence under 975 nm laser excitation with UCL spectra showing two main green bands around 529 nm (Er3+, 2H11/2 → 4I15/2) and 551 nm (Er3+, 4S3/2 → 4I15/2), in addition to a very weak one at 655 nm (Er3+, 4F9/2 → 4I15/2). The (N/L)­BMO:Yb3+,Ho3+ mainly showed a green band around 544 nm (5S2,5F4 → 5I8) and a red band around 654 nm (5F5 → 5I8) upon 975 nm laser excitation. With increasing Yb3+ concentrations in (N/L)­BMO:Yb3+,0.01Ho3+, the red/green ratios decreased monotonously corresponding to the emission color variation from light red to light yellow. Both UCL mechanisms of Yb3+,Er3+ and Yb3+,Ho3+ were determined to be two-phonons absorption processes in (N/L)­BMO:Yb3+,Er3+/Ho3+. The Ce3+ ions were introduced into Yb3+,Ho3+ codoped (N/L)­BMO to show the color tuning from light yellow to light red originating from the cross relaxation processes of (CR1) Ho3+ (5F4,5S2) + Ce3+ (2F5/2) → Ho3+ (5F5) + Ce3+ (2F7/2) and (CR2) Ho3+(5I6) + Ce3+ (2F5/2) → Ho3+ (5I7) + Ce3+ (2F7/2), which is based on the energy matching of Ce3+2F7/2-2F5/2 level pairs with Ho3+5I6-5I7 and 5F4,5S2-5F5 level pairs and confirmed by the decay times. These results suggest good UCL properties of (N/L)­BMO:Yb3+, Er3+ and (N/L)­BMO:Yb3+, Ho3+, Ce3+ materials, and color modulation is easily controlled by varying Yb3+ concentration and a cross relaxation process between Ce3+ and Ho3+, which provides efficient methods to regulate the emission color of UCL phosphors.

Insight into the Luminescence Alternation of Sub‐30 nm Upconversion Nanoparticles with a Small NaHoF4 Core and Multi‐Gd3+/Yb3+ Coexisting Shells

“…[ 48–50 ] To reduce the green/red (G/R) ratio for purer red emission, Ce 3+ is normally employed for its CR processes with Ho 3+ , which could increase the population of excited states 5 I 7 and 5 F 5 of Ho 3+ to promote the red emission. [ 51–57 ] In addition to this, other techniques involving high excitation power [ 58,59 ] or unwonted types of laser with specific parameters [ 60,61 ] could also implement high purity of red UCL, which actually gets unsuitable or too complicated for biouse. In this sense, exploring more targeted strategies would bring out more flexibility for Ho‐based UCL materials to distinguish themselves.…”

Antiferromagnetism of Double Molybdate LiFe(MoO4)2

“…The inclusion of Li ion at A site make them suitable to be used in lithium-ion batteries as anode materials, while the W/Mo can provide a relative large spin-orbit coupling considering its 4d/5d orbitals 1,[6][7][8][9] . Most importantly, the B-site ions with narrow bands can provide other applicable physical properties, such as magnetism and luminescence [10][11][12][13][14][15] .…”

A novel Sm3+-activated Li3BaSrLn3(MO4)8 [Ln = La, Gd, and Y; M = Mo and W] deep red-emitting phosphors for plant cultivation and white LEDs

“…To overcome these defects and thereby improve the CRI and white LED device efficiency, new host lattices that have high thermal stability and IQE must be found. The molybdate host lattice is considered a good host matrix for Ln 3+ -based luminescent materials due to its high thermal quenching behavior and chemical stability [16]. Recently, the research group developed an Eu 3+activated red phosphor with an Li 3 BaSrLa 3 (MoO 4 ) 8 host lattice.…”