Dhaval Modi

Hydrothermal synthesis and photoluminescence properties of cerium-doped cadmium tungstate nanophosphor

The present paper reports synthesis and photoluminescence studies of cadmium tungstate (CdWO4) and cerium-doped cadmium tungstate. The samples were synthesised by low cost and low temperature hydrothermal method and characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence analysis. XRD pattern reveals that the CdWO4 has monoclinic wolframite structure. The FTIR spectrum of cerium-doped CdWO4 exhibits broadband below 700 cm−1 which is due to the δ (Ce–O–C) mode. The TEM images show that size of particle is approximately 60–120 nm in both samples. A broad intense peak was observed at 474 nm when the samples were excited with 263 nm. A broad intense peak was observed at 475 nm when the samples were excited with 600 nm. The intensity of the 474 nm peak decreases with increase in cerium doping concentration. The observation of 475 nm peak when excited with 600 nm is upconversion luminescence. This upconversion emission is due to energy transfer upconversion process involving Cd2+ ions and [WO6]6− ions. Ce3+ ion is responsible for the peak shift of 6 nm.

Luminescence study and dosimetry approach of Ce on an α-Sr2P2O7 phosphor synthesized by a high-temperature combustion method

We report synthesis of a cerium-activated strontium pyrophosphate (Sr2 P2 O7 ) phosphor using a high-temperature combustion method. Samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and thermoluminescence (TL). The XRD pattern reveals that Sr2 P2 O7 has an α-phase with crystallization in the orthorhombic space group of Pnam. The IR spectrum of α-Sr2 P2 O7 displays characteristic bands at 746 and 1190 cm(-1) corresponding to the absorption of (P2 O7 )(-4) . PL emission spectra exhibit a broad emission band around 376 nm in the near-UV region due to the allowed 5d-4f transition of cerium and suggest its applications in a UV light-emitting diode (LED) source. PL also reveals that the emission originates from 5d-4f transition of Ce(3+) and intensity increases with doping concentration. TL measurements made after X-ray irradiation, manifest a single intense glow peak at around 192°C, which suggests that this is an outstanding candidate for dosimetry applications. The kinetic parameters, activation energy and frequency factor of the glow curve were calculated using different analysis methods.

Thermoluminescence kinetic features of Eu3+ doped strontium pyrophosphate after beta irradiation

Strontium pyrophosphate (Sr2P2O7) doped with various concentrations of Eu3+ as a doping agent is synthesized using a combustion method and to study the thermoluminescence dosimetry [TLD] and applications. The synthesized phosphors with different concentrations of doping ions were irradiated using a 90Sr β-source for different doses from 5 Gy to 50 Gy. TL glow curves of all the samples were measured with a heating rate of 6 K s−1 from room temperature [325] to 550 K. Each time 5 mg of irradiated phosphor was taken for TL measurement. The TL exhibited by the phosphor shows a single bell-shaped curve at a peak temperature of around 415 to 420 K. From the TL glow curves the kinetic parameters of phosphors were calculated using the initial rise method (IR), whole glow peak method, peak shape method (PSM) and Kitis et al. second-order equation and also necessary statistical analysis was done. The TL glow curve parameters like activation energy (Ea), frequency factor (s) and order of kinetics (b) found from all analytical methods of all beta irradiated phosphor samples revealed that the glow curves have second-order kinetics with an activation energy of 0.90–1.10 eV and a frequency factor 1010 to 1011 s−1. All samples showed a linear response of TL as a function of dose from 5 Gy to 50 Gy. The sensitivity, fading effect and TL glow curve shape are unaffected by the doping concentration which implies that the phosphor shows consistent TL output except for intensity variation. The calculated TL parameters and results are consistent and well matched with the theoretical aspects.

Characteriztion and luminescence studies of Dysprosium Titanate by two synthesis methods

The present paper reports Phase analysis and luminescence studies of Dysprosium Titanate phosphor which was synthesized by hydrothermal and combustion methods. The synthesized samples were characterized by X-ray diffraction technique (XRD), Fourier Transmission Infrared Spectroscopy (FTIR) and Photoluminescence (PL). XRD spectra reveal that both samples of Dy2Ti2O7 were highly crystalline in nature. In XRD analysis, it is observed that two different phases have been obtained and it is attributed to different synthesizing methods. FT-IR was utilized to monitor the structural changes of compounds during the preparative process. Room Temperature Photoluminescence spectra recorded at 254 nm excitation wavelength show, broad emission in UV-blue region. The exhibited peaks at 474 nm and 484 nm are attributed to the transitions 4F9/2 to 6H15/2 of Dy+3. PL emission spectra were fitted with four individual Gaussian peaks.

Optical properties of Eu(III) doped strontium gadolinium niobate oxide

Sr2GdNbO6 doped with trivalent ion of Eu phosphors having monoclinic phase of space group P21/n have been synthesized via solid state reaction method, and their photoluminescence properties have been examined under UV excitation. The emission peaks exhibited around 580, 596, and 610nm wavelength. By using xenon lamp as a source of excitation having wavelengths at 254 and 262nm, it is observed that the maximum light emission yielded in red region. It is inferred that the dopant Eu+3 ions may take the substitutional positions at non-centrosymmetric site.

The effect of Tb+3 on α-Sr2P2O7 phosphor for green LED phosphor application

A series of Tb+3 activated α-Sr2P2O7 (Strontium Pyrophosphate) phosphors were synthesized by high temperature combustion synthesis method. The structural analysis has been done by x-ray diffraction and FTIR (Fourier Transform Infrared Spectrum). The results obtained in structural characterization indicate that the doping concentration did not affect the crystal phase and structure of the phosphors. X-ray diffraction pattern reveals that the all samples were consistence with the JCPDS card No. 24-1011. The phosphor was excited at 232 nm wavelength, very intense PL green emission peak have been observed at 545 nm. This illustrates, that the phosphors could be efficiently excited because of the charge transfer band of the host as well as the energy transfer process occurred between host (Sr2P2O7) and activator (Tb+3). By increasing the doping concentration of Tb+3, the intensity of 545 nm emission peak has been increased predominantly and it suggest that the phosphor prepared has very good application in gre...