Structural and spectroscopic characterization of a new series of Ba₂RE₂Ge₄O₁₃(RE = Pr, Nd, Gd, and Dy) and Ba₂Gd_2−xEu_xGe₄O₁₃tetragermanates

Abstract

A new series of Ba2RE2Ge4O13 (RE = Pr, Nd, Gd, Dy) germanates and Ba2Gd2-xEuxGe4O13 (x = 0.1–0.8) solid solutions have been synthesized using solid-state reaction technique and characterized by X-ray...

Reddish-orange emitting Eu2−x Gd x Ge2O7 pyrogermanate ceramic phosphors: synthesis and role of Eu3+/Gd3+ substitution on the optical features

“…For clarity, figure 7 presents a partial energy levels diagram of Gd 3+ and Eu 3+ . In addition, Eu 3+ f -f bands (circles) are observed at 318, 327, 361, 381, 392, 394, 415, 463, 525, and 533 nm, which can be attributed to the transitions from ground-state 7 F 0 to the 5 H 4 , 5 H 3 , 5 D 4 , 5 L 7 , 5 L 6, 5 L 6 , 5 D 3 , 5 D 2 , and 5 D 1 excited states, and 5 D 1 ← 7 F 1 , respectively, in agreement with previous works [6,26,28,29,35,47,48]. A broadband centered at approximately 260 nm emerges all spectra in figure 6(a), which corresponds to O 2− → Eu 3+ CTB.…”

“…Besides that, it was only possible to perceive the mistake when the Eu 2−x Gd x Ge 2 O 7 solid solution series was studied. Thus, the values obtained for the samples of Pr, Tb, and Yb by Martins et al [28] may be underestimated due to interference from other electronic transitions [26,40,44,45].…”

“…Gupta et al [25] reported a high-pressure analysis of Gd 1.99 Eu 0.01 Hf 2 O 7 emissions, being capable of choosing the emitting color by pressure variation. This lanthanide pair combination was also investigated in a tetragermanate host (Ba 2 Gd 2−x Eu x Ge 4 O 13 ) by Lipina et al [26] and presented promising features in photonic applications, ratifying a great perspective in Eu-Gd combined with Ge hosts [24,27]. High potential for application as red phosphors suitable in a large UV region of excitation has been demonstrated for pyrogermanate materials containing Eu-Gd, which have band gap energies around 5.60-5.90 eV [28,29].…”

Structural, electronic and optical properties of BaRE6(Ge2O7)2(Ge3O10) (RE = Tm, Yb, Lu) compounds and BaYb6(Ge2O7)2(Ge3O10):Tm3+ and BaLu6(Ge2O7)2(Ge3O10):Yb3+,Tm3+ phosphors: potential applications in temperature sensing

“…Moreover, excellent thermal and chemical stability, hardness and large transparency make germanates favorable hosts for creating efficient persistent luminescent materials and phosphors for LEDs. [8][9][10][11][12][13][14][15][16] In this work, we report a new BaRE 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ) family, containing both [Ge 2 O 7 ] and [Ge 3 O 10 ] groups in the structure. The crystal/electronic structures and optical properties of these germanates are discussed in detail.…”

“…Moreover, excellent thermal and chemical stability, hardness and large transparency make germanates favorable hosts for creating efficient persistent luminescent materials and phosphors for LEDs. 8–16…”