Synthesis process and luminescence properties of Tm3+ in AWO4 (A=Ca, Sr, Ba) blue phosphors

Room temperature ferromagnetism and enhanced optical property of Yb doped SrWO 4 compounds have been investigated for the importance in the field of spintronics. Pristine and Yb doped SrWO 4 compounds were synthesized by simple chemical precipitation method. Powder X-ray diffraction analysis reveals the scheelite type tetragonal structure of all the prepared compounds. The crystallite size and lattice strain was calculated by Williamson-Hall plot. The local structural disorder of the compounds was investigated by Laser Raman spectroscopy and it was found that the local disorder induced by the dopant leads to alteration in Raman active modes of Yb doped SrWO 4 compounds. The formation of microsphere and platelets like shapes of particulate system was examined by electron microscopy techniques. The evidences for oxygen vacancy and oxidation states of elements present in the compounds were analyzed by X-ray photoemission spectroscopy. In UV-Vis spectra, distinctive shift of absorption edge was observed exclusively for all the Yb doped SrWO 4 compounds. The presence of defective states with prominent blue and green emission of the compounds was investigated by photoluminescence spectroscopy. Magnetization study reveals that the pristine SrWO 4 compound exhibits unsaturated ferromagnetic behaviour, whereas all the Yb doped SrWO 4 compounds demonstrates saturated ferromagnetic behaviour. The enhancement of magnetization and ferromagnetic ordering of the compounds has been explained in terms of carrier-induced Ruderman-Kittel-KasuyaYosida interaction theory. Hence, from the present investigation it was observed that the doping of Yb in SrWO 4 will yields a new kind of multifunctional material for fabricating magneto-optical and electronic devices.

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Band gap tailoring and enhanced ferromagnetism in Yb doped SrWo4 scheelite structured system

Muralidharan

Anbarasu

Perumal

et al. 2015

“…Among various AWO 4 materials, Strontium Tungstate (SrWO 4 ) has attracted a great deal of attention in recent years because of their intriguing luminescence and structural properties [24][25][26][27]. SrWO [17,18,27].…”

Section: Introductionmentioning

confidence: 99%

Studies on multifunctional behaviour of Cr doped SrWO4 Compounds

Muralidharan

Anbarasu

Perumal

et al. 2015

Transition metal doped divalent tungstate compounds endowed with coalescence of optical and magnetic property forms a class of multifunctional materials and found importance in the field of magneto-optical and spintronics device applications. In the present work, pure and Cr doped SrWO 4 compounds were synthesized by chemical precipitation method. Powder X-ray diffraction analysis reveals scheelite type tetragonal structure of all the compounds. The effect of doping on crystal symmetry and local structure of the compounds was investigated by Laser Raman spectroscopy studies. The micro sphere and polydispersed surface morphology of all the compounds were examined by scanning electron microscopy and transmission electron microscopy analysis. Further, the evidences for oxygen vacancy and oxidation states of elements present in the compounds were analyzed by X-ray photoelectron spectroscopy. The optical absorption spectra explicitly describe the distinctive shift in absorption edge and linear decrease in band gap values while increasing Cr concentrations in SrWO 4 system. The presence of defective states and oxygen vacancy in Cr doped SrWO 4 compounds were confirmed with multicolor PL emission spectra. Electron paramagnetic resonance spectra authenticates the inducement of paramagnetic center (Cr 3? ) on increasing the dopant concentration. The magnetization analysis demonstrates enhanced ferromagnetic behaviour of all the Cr doped compounds, whereas the pure SrWO 4 compound exhibits frustrated ferromagnetic behaviour. The augmented ferromagnetic ordering in Cr doped compounds has been explained in terms of carrier-induced RudermanKittel-Kasuya-Yosida interaction theory. The possible inducement of carrier mediated room temperature ferromagnetism in Cr doped SrWO 4 explicit demonstrates a hopeful candidature for magneto-optical and spintronic device applications.

“…However, the luminescence properties of this superior phosphor could be varied by doping with rare earth ions [10][11][12][13][14][15][16][17][18][19][20][21]. It is known that samarium (Sm 3? )…”

Section: Introductionmentioning

confidence: 99%

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

Yang

Wang

et al. 2014

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.