Ishwar Prasad Sahu

Structural characterization and optical properties of Ca2MgSi2O7:Eu2+,Dy3+ phosphor by solid-state reaction method

Ca2MgSi2O7:Eu(2+),Dy(3+) phosphor was prepared by the solid-state reaction method under a weak reducing atmosphere. The obtained phosphor was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FT-IR) techniques. The phase structure of the Ca2MgSi2O7:Eu(2+),Dy(3+) phosphor was akermanite type, which is a member of the melilite group. The surface morphology of the sintered phosphor was not uniform and phosphors aggregated tightly. EDX and FT-IR spectra confirm the elements present in the Ca2MgSi2O7:Eu(2+),Dy(3+) phosphor. Under UV excitation, a broadband emission spectrum was found. The emission spectra observed in the green region centered at 535 nm, which is due to the 4f-5d transition. The mechanoluminescence (ML) intensity of the prepared phosphor increased linearly with increases in the mechanical load. The ML spectra were similar to the photoluminescence (PL), which indicates that ML is emitted from the same emitting center of Eu(2+) ions as PL.

Photoluminescence properties of europium doped di-strontium magnesium di-silicate phosphor by solid state reaction method

Abstract Europium doped di-strontium magnesium di-silicate phosphor namely (Sr2MgSi2O7:Eu3+) was prepared by the traditional high temperature solid state reaction method. The phase structure of sintered phosphor was akermanite type structure which belongs to the tetragonal crystallography with space group , this structure is a member of the melilite group and forms a layered compound. The EDX and FTIR spectra confirm the present elements in Sr2MgSi2O7:Eu3+ phosphor. Photoluminescence measurements showed that the phosphor exhibited strong emission peak with good intensity, corresponding to 5D0 → 7F2 (613 nm) red emission and weak 5D0 → 7F1 (590 nm) orange emission. The excitation spectra monitored at 613 nm show broad band from 220 to 300 nm ascribed to O–Eu charge-transfer band (CTB) centered at about 269 nm, and the other peaks in the range of 300–400 nm originated from f–f transitions of Eu3+ ions. The strongest band at 395 nm can be assigned to 7F0 / 5L6 transition of Eu3+ ions due to the typical f–f transitions within Eu3+ of 4f6 configuration.

Luminescence properties of green-emitting Ca2MgSi2O7:Eu2+ phosphor by a solid-state reaction method.

A europium (Eu)-doped di-calcium magnesium di-silicate phosphor, Ca2MgSi2O7 :Eu(2+) , was prepared using a solid-state reaction method. The phase structure, particle size, surface morphology, elemental analysis, different stretching mode and luminescence properties were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL) and mechanoluminescence (ML). The phase structure of Ca2MgSi2O7:Eu(2+) was an akermanite-type structure, which belongs to the tetragonal crystallography with space group P4̅21 m; this structure is a member of the melilite group and forms a layered compound. The surface of the prepared phosphor was not found to be uniform and particle distribution was in the nanometer range. EDX and FTIR confirm the components of Eu(2+)-doped Ca2MgSi2O7 phosphor. Under UV excitation, the main emission peak appeared at 530 nm, belonging to the broad emission ascribed to the 4f(6) 5d(1) → 4f(7) transition of Eu(2+). The ML intensity of the prepared phosphor increased linearly with increasing impact velocity. A CIE color chromaticity diagram and ML spectrum confirmed that the prepared Ca2MgSi2O7:Eu(2+) phosphor would emit green color and the ML spectrum was similar to that of PL, which indicated that ML is emitted from the same center of Eu(2+) ions.

Europium doped di-calcium magnesium di-silicate orange–red emitting phosphor by solid state reaction method

Abstract A new orange–red europium doped di-calcium magnesium di-silicate (Ca2MgSi2O7:Eu3+) phosphor was prepared by the traditional high temperature solid state reaction method. The prepared Ca2MgSi2O7:Eu3+ phosphor was characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) with energy dispersive x-ray spectroscopy (EDX), fourier transform infrared spectra (FTIR), photoluminescence (PL) and decay characteristics. The phase structure of sintered phosphor was akermanite type structure which belongs to the tetragonal crystallography with space group , this structure is a member of the melilite group and forms a layered compound. The chemical composition of the sintered Ca2MgSi2O7:Eu3+ phosphor was confirmed by EDX spectra. The PL spectra indicate that Ca2MgSi2O7:Eu3+ can be excited effectively by near ultraviolet (NUV) light and exhibit bright orange–red emission with excellent color stability. The fluorescence lifetime of Ca2MgSi2O7:Eu3+ phosphor was found to be 28.47ms. CIE color coordinates of Ca2MgSi2O7:Eu3+ phosphor is suitable as orange-red light emitting phosphor with a CIE value of (X=0.5554, Y=0.4397). Therefore, it is considered to be a new promising orange–red emitting phosphor for white light emitting diode (LED) application.

Enhancement of the photoluminescence and long afterglow properties of Ca2MgSi2O7:Eu2+ phosphor by Dy3+ co-doping

Sr2MgSi2O7:Eu(2+) and Sr2MgSi2O7:Eu(2+),Dy(3+) long afterglow phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and photo-, thermo- and mechanoluminescence spectroscopic techniques. The phase structure of the sintered phosphor was an akermanite type structure, which belongs to tetragonal crystallography. The thermoluminescence properties of these phosphors were investigated and compared. Under ultraviolet light excitation, the emission spectra of both prepared phosphors were composed of a broad emission band peaking at 470 nm. When the Sr2MgSi2O7:Eu(2+) phosphor was co-doped with Dy(3+), the photoluminescence (PL), afterglow and mechanoluminescence (ML) intensity were strongly enhanced. The decay graph indicated that both the sintered phosphors contained fast decay and slow decay processes. The ML intensities of Sr2MgSi2O7:Eu(2+) and Sr2MgSi2O7:Eu(2+),Dy(3+) phosphors were increased proportionally with increasing impact velocity, a finding that suggests that these phosphors could be used as sensors to detect the stress of an object.

Impulsive excitation of mechanoluminescence in europium activated strontium ortho-silicate phosphor

Europium doped strontium ortho-silicate (Sr2SiO4:Eu2+) phosphor was prepared by the traditional high temperature solid state reaction method. The crystal structure of sintered phosphor was consistent with the orthorhombic crystallography with space group Pmna. The surface of the prepared phosphor was not found to be uniform and particle distribution in different size. An energy dispersive X-ray spectroscopy (EDS) spectrum confirms the presence of elements in sintered phosphor. The mechanoluminescence (ML) intensity of Sr2SiO4:Eu2+ phosphor increases linearly with increasing impact velocity of the moving piston which suggests that these phosphors can be used as sensors to detect the stress of an object. Thus, the present investigation indicates the piezo-electricity is responsible to produce ML in prepared Sr2SiO4:Eu2+ phosphor. The time of the peak ML intensity and the decay rate did not change significantly with respect to increasing impact velocity of the moving piston and peak ML intensity increases linearly.

Structural Characterization of Gd 2 O 3 Phosphor Synthesized by Solid-State Reaction and Combustion Method Using X-Ray Diffraction and Transmission Electron Microscopic Techniques

The combustion synthesis and conventional solidstate reaction method was used to synthesize Gadolinium oxide (Gd2O3) phosphor. Nanoranged Gd2O3 was successfully synthesized by ignition of gadolinium nitrate followed by combustion in the presence of urea, and for the solid-state reaction method, boric acid was used as a flux at high temperature of 1400°C monoclinic and cubic phase gadolinium oxide (Gd2O3) phosphor was obtained for combustion and solid-state reaction method, respectively. Samples prepared by both the methods were characterized by using X-ray diffraction (XRD) spectroscopy, and transmission electron microscopy (TEM). The crystallite size and grain size of these phosphors are compared by using XRD profile analysis as well as by TEM. Other physical parameters such as strain, stress, and deformation energy density are also estimated precisely for the prominent XRD peaks of Gd2O3 powder in the range 2θ by using a modified Williamson-Hall analysis assuming uniform deformation model.

Ca2Al2SiO7:Ce3+ phosphors for mechanoluminescence dosimetry

A series of Ce3+ ion single-doped Ca2 Al2 SiO7 phosphors was synthesized by a combustion-assisted method at an initiating temperature of 600 °C. The samples were annealed at 1100 °C for 3 h and their X-ray diffraction patterns confirmed a tetragonal structure. The phase structure, particle size, surface morphology and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. Thermoluminescence (TL) intensity increased with increase in ultraviolet (UV) light exposure time up to 15 min. With further increase in the UV irradiation time the TL intensity decreases. The increase in TL intensity indicates that trap concentration increased with UV exposure time. A broad peak at 121 °C suggested the existence of a trapping level. The peak of mechanoluminescence (ML) intensity versus time curve increased linearly with increasing impact velocity of the moving piston. Mechanoluminescence intensity increased with increase in UV irradiation time up to 15 min. Under UV-irradiation excitation, the TL and ML emission spectra of Ca2 Al2 SiO7 :Ce3+ phosphor showed the characteristic emission of Ce3+ peaking at 400 nm (UV-violet) and originating from the Ce3+ transitions of 5d-4f (2 F5/2 and 2 F7/2 ). The photoluminescence (PL) emission spectra for Ca2 Al2 SiO7 :Ce3+ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca2 Al2 SiO7 :Ce3+ phosphor for radiation dosimetry are discussed. Copyright

Studies on the luminescence properties of cerium co-doping on Ca2MgSi2O7:Eu2+ phosphor by solid-state reaction method

Ca2 MgSi2 O7 :Ce3+ , Ca2 MgSi2 O7 :Eu2+ and Ca2 MgSi2 O7 :Eu2+ ,Ce3+ phosphors were prepared using the solid-state reaction method. The crystal structures of the sintered phosphors were of melilite type, which has a tetragonal crystallography. The chemical compositions of the sintered phosphors was confirmed by energy dispersive X-ray spectroscopy. The different thermoluminescence kinetic parameters [activation energy (E), frequency factor (s) and order of the kinetics (b)] of these phosphors were evaluated and compared using the peak shape method. Under ultraviolet excitation, the emission spectra of both Ca2 MgSi2 O7 :Eu2+ and Ca2 MgSi2 O7 :Eu2+ ,Ce3+ phosphors were composed of a broad emission band peaking at 530 nm. When the Ca2 MgSi2 O7 :Eu2+ phosphor is co-doped with Ce3+ ions, photoluminescence, afterglow and mechanoluminescence intensity was strongly enhanced. Ca2 MgSi2 O7 :Eu2+ showed some afterglow with a short persist time. On incorporation of Ce3+ , efficient energy transfer from Ce3+ to Eu2+ was found and the emission intensity of Eu2+ was enhanced. The mechanoluminescence intensities of Ca2 MgSi2 O7 :Ce3+ , Ca2 MgSi2 O7 :Eu2+ and Ca2 MgSi2 O7 :Eu2+ ,Ce3+ phosphors increased proportionally increased with the increase in impact velocity, which suggests that these phosphors can be used as sensors to detect stress in an object.