NaBi_0.9Eu_0.1(MoO₄)₂ Nanomaterials: Tailoring the Band Gap and Luminescence by La³⁺ Substitution for Light-Emitting Diodes

Abstract

Nanomaterials of NaBi0.9Eu0.1(MoO4)2 were prepared by a simple coprecipitation method in ethylene glycol medium at room temperature. Substitution of bismuth with lanthanum resulted a single-phase solid solution (NaBi0.9–x La x Eu0.1(MoO4)2, 0.0 ≤ x ≤ 0.9) in the complete range of compositions. The linear relationship observed for unit cell parameters, Raman shifts, and FTIR peak positions with lanthanum concentration confirmed the solid solution formation. The band gap of the NaBi0.9–x La x Eu0.1(MoO4)2 nanomaterials widens from 3.36 to 4.4 eV with increasing La3+ concentration in these solid solutions. These nanomaterials show strong red emission upon excitation with UV–visible light. The emission properties of Eu3+ are improving with increasing the La3+ content. The band gap of the solid solution plays a crucial role in the improvement of emission properties and is highly dependent on the excitation wavelength. This improvement is marginal while exciting with 464 nm light due to the reduction in the inter Eu3+ ion energy transfer brought by the lattice expansion, whereas drastic improvement is observed when exciting at 280 and 394 nm light due to the combined effect of band gap and lattice expansion. The quantum efficiency estimated from emission spectra and excited state lifetime values revealed that NaLa0.9Eu0.1(MoO4)2 nanomaterials are best in the series with ∼70% efficiency. These materials can be a suitable red phosphor for white light-emitting diodes (WLEDs)

Excitation dependent visible and NIR photoluminescence properties of Er3+, Yb3+ co-doped NaBi(MoO4)2 nanomaterials

“…Recently, reports on lanthanide doped bismuth based nanomaterials are increasing gradually due to its advantages over rare earths such as nontoxic nature, more abundant, less expensive and an environment ecofriendly, which could be termed as 'Green Bismuth'. [17][18][19][20][21][22][23][24][25][26][27] Also, ionic size, charge, coordination number of bismuth is similar to rare earth ions. Bismuth activated materials are known to have their characteristic emission properties which makes them more important class of luminescent materials.…”

Structural and Excitation-Dependent Photoluminescence Properties of Bi0.95–xGdxEu0.05PO4 (0 ≤ x ≤ 0.95) Solid Solutions and Their Anticounterfeiting Applications

“…These results further strengthen the conclusions drawn from XRD studies. The band gap of the nanomaterials was calculated using the following formula where ν is the frequency of the incident light, h is Planck’s constant, E g is the band-gap energy, A is a proportionality constant, and F ( R ) is the Kubelka–Munk (KM) function. The KM function is defined as F ( R ) = (1 – R ∞ ) 2 /2 R ∞ , where R ∞ is the diffuse reflectance of the sample normalized to the nonabsorbing standard.…”

“…The spontaneous emission cross section ( A 0– J ) of 5 D 0 → 7 F J ( J = 1, 2, 3, 4) transitions is calculated from the Eu 3+ emission spectrum using the following equation where ν 0– J is the frequency of the 0– J spectral transition and I 0– J is the integrated peak intensity of the 0– J transition of Eu 3+ emission. A 0–1 is the spontaneous emission cross section of 0–1 transition and is constant (50 s –1 ). , The integrated peak intensity at different excitation wavelengths as a function of Gd 3+ concentration ( x ) is shown in Figure S7d–f.…”

A review on the structural dependent optical properties and energy transfer of Mn4+ and multiple ion-codoped complex oxide phosphors

“…The PLE spectrum monitored at 714 nm consists of two strong excitation peaks centered at 340 and 484 nm, which are attributed to the spin-allowed 4 A 2g / 4 T 1g and 4 A 2g / 4 T 2g transitions of Mn 4+ , respectively. [148][149][150][151][152] The obvious spectral overlap between the Ln 3+ emission band and Mn 4+ excitation band indicates the possible resonant energy transfer from Ln 3+ to Mn 4+ . As evidenced in Fig.…”