Effects of co-doped Li+ ions on luminescence of CaWO4:Sm3+ nanoparticles

Abstract

CaWO 4 , CaWO 4 :Sm 3? and CaWO 4 :(Sm 3? , Li ? ) nanoparticles were synthesized by the precipitation method with addition of PEG 200. The X-ray diffraction patterns show that the obtained samples have a pure tetragonal phase. The CaWO 4 sample shows an emission peak at 418 nm originating from the charge-transfer transitions within the WO 4 2-complex. CaWO 4 :Sm 3? and CaWO 4 :(Sm 3? , Li ? ) samples show emission peaks originating from the f-f forbidden transitions of the 4f electrons of Sm 3? ions. The charge compensator of Li ? can enhance the emission intensity effectively. It is found that the emission intensity of CaWO 4 :(3 mol% Sm 3? , 4 mol% Li ? ) phosphor is about double that of CaWO 4 :3 mol% Sm 3? phosphor.

Electrical properties of Dy3+/Na+ Co-doped oxide thermoelectric [Ca1-x(Na1/2Dy1/2)x]MnO3 ceramics

“…On the other hand, compared with the data of single Dydoped CaMnO 3 system, the electrical resistivity is clearly higher, especially when x ¼ 0.05 and 0.10, which could be explained by the hypothesis that doping þ3 and þ 1 valence dopants could decrease the variation of carrier concentration to a certain extent [19,22]. More specifically, the holes introduced by doping Na þ compensated the electrons introduced by doping Dy 3þ , leading to a charge balance, which refers to the low variation of carrier concentration when compared to single Dy-doped system [12,13]. With the increase of (Dy 1/2 Na 1/2 ) content, considering that Na partially volatilized during the sintering process and became insufficient compared with Dy, the second phase became more clearly and the function of carrier offset caused by simultaneously doping Na þ and Dy 3þ receded.…”

“…Dy 3þ performed as the n-type doping leading to a high electron concentration while Na þ acted as the p-type doping for increasing the hole concentration. These holes introduced by doping Na þ could compensate the electrons introduced by doping Dy 3þ [12,13]. In other words, doping Dy 3þ and Na þ simultaneously would not introduce as many electrons as the single Dy-doped system do, which means a relatively low resistivity could be obtained and the Seebeck coefficient could be maintained at a relatively high level, leading to a high PF.…”

Morphology-controlled synthesis of NaGd(WO4)2:Eu3+ microcrystals by hydrothermal process

“…6 gives the excitation spectra of obtained NaGd(WO 4 ) 2 :Eu 3+ samples with addition of PVP and Na 3 Cit. Clearly, excitation spectra of NaGd(WO 4 the range of 275-350 nm in the excitation spectra. These shoulders should originate from the overlaps of the 8 S ?…”

“…The tungstate and double tungstate families have been long known as functional materials and have been used in some fields because of their luminescence properties corresponding to the electron transitions within the 4f shell, such as CaWO 4 [3][4][5], PbWO 4 [6], CdWO 4 [7], BaWO 4 [8,9], KY(WO 4 ) 2 : Yb 3+ [10], NaLaWO 4 [11], K 1Àx Na x Gd(WO 4 ) 2 [12] and NaGd(WO 4 ) 2 [13]. In recent years, one of important applications of tungstates and double tungstates is to be as host materials for rare earth (RE) ions.…”

ABO4 type scheelite phases in (Ca/Sr)MoO4 - BiVO4 - Bi2Mo3O12 systems: synthesis, structure and optical properties

“…)[16][17]6];(3) formation of cation vacancies (A 1-3x M 2x Ф x BO 4 ) [13-17]. Mechanism (3) was reported for rare earth molybdates Ln 2 Mo 3 O 12 (Ln 2/3 MoO 4 ,…”