Luminescence Properties of Sr2MgSi2O7:Eu2+, Ce3+ Phosphor by Solid State Reaction Method

AbstractThe Sr2MgSi2O7:Eu2+, Ce3+ phosphor was prepared by solid state reaction method, boric acid (H3BO3) was added as flux. The phase structure of Sr2MgSi2O7:Eu2+, Ce3+ 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 layered compound. EDX and FTIR spectra confirm the present elements in Sr2MgSi2O7:Eu2+, Ce3+ phosphor. Three peaks in excitation spectra were found at 253, 293, 325nm and corresponding emission peak was recorded at 465nm, belonging to the broad emission ascribed to the 4f65d1→4f7 transition of Eu2+. The ML intensity of prepared phosphor was increasing linearly with increases of mechanical load

Thermoluminescence of Cu doped ZnS nanoparticles

ZnS nanoparticles doped with Cu were synthesized by wet chemical route method at 4°C temperature. We have investigated the Thermoluminescence (TL) properties of the undoped ZnS and Cu doped ZnS with increase in Cu concentration from 0.5 millimole to 1.5 millimole and also study for different weight of Sodium Hexa Meta Phosphate (SHMP) capping agent from 2gm to 10gm. The XRD studies indicate that most of the samples are cubic in nature. The broadening of peaks tends to increase with increasing weight of capping agent showing decrease in particle size. The crystalline size computed using Scherer formula is found 2nm to 3nm. Absorption spectra show blue shift with different weight of capping agent. TL glow curve shows a single peak at 543 K temperature. Variation in TL intensity as a function of copper concentration is studied and 1mM is found to be the optimum concentration for TL. The trap parameters namely, activation energy (E), order of kinetics (b) and frequency factor(s) of ZnS: Cu sample have been determined using Chen’s method. The effect of heating rates and UV radiation dose for different time on TL glow curve has also been studied

Mechanoluminescence properties of SrAl2O4: Tb3+ phosphor

Through the execution of experimental investigation, Mechanoluminescence of SrAl2O4:Tb3+ phosphor was studied which is synthesized by combustion method. In the observation, the peak value of ML depends on the different impact velocity. It was seen that at 55 cm height, the maximum peak of ML is obtained.&nbsp

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

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 P4¯21m, 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 28.47 ms. 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

UV and gamma ray induced thermoluminescence properties of cubic Gd2O3:Er3+ phosphor

This paper reports the thermoluminescence properties of Er3+ doped gadolinium oxide nanophosphor. The phosphor is prepared by high temperature solid state reaction method. The method is suitable for large scale production. Starting materials used for sample preparation were Gd2O3, Er2O3 (0.5–2.5 mol%) and fixed concentration of boric acid using as a flux. The prepared samples were characterized by X-ray diffraction technique and the particle size calculated by Scherer's formula. The surface morphology of prepared phosphor is determined by scanning electron microscopic (SEM) technique. Functional group analysis was done by Fourier transform infra-red spectroscopy (FTIR) analysis. The elemental analysis of prepared sample was determined by energy dispersive X-ray analysis (EDX) and the exact particle size of prepared phosphor for the different concentration of dopant (Er3+) was evaluated by transmission electron microscopy (TEM) technique. The prepared phosphors for different concentration of Er3+ were examined by thermoluminescence (TL) glow curve for UV and gamma irradiation. The UV 254 nm source was used for UV irradiation and Co60 source was used for gamma irradiation. The samples show well resolved broad peak covered the temperature range 50–250 °C and the peak temperature found at 126 °C for UV irradiation and higher temperature peak at 214 °C for gamma irradiation. The effect of heating rate on TL studies was presented for optimized sample. Here UV irradiated sample shows the formation of shallow trap (surface trapping) and the gamma irradiated sample shows the formation of deep trapping. The estimation of trap formation was evaluated by knowledge of trapping parameters. The trapping parameters such as activation energy, order of kinetics and frequency factor were calculated by peak shape method. Here most of the peak shows second order of kinetics. The effect of gamma and UV exposure on TL studies was also examined and it shows linear and sublinear response with dose which indicates that the sample may be useful for TL dosimetry. Keywords: Thermoluminescence, Gamma irradiation, UV irradiated, TL dosimetry, Activation energy, Order of kinetics, Frequency facto

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

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 P42¯1m, 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 studies on the europium doped strontium metasilicate phosphor prepared by solid state reaction method

Europium doped strontium meta-silicate (namely SrSiO3:Eu3+) phosphor was prepared by a high temperature solid state reaction method. The sintered SrSiO3:Eu3+ phosphor possesses a monoclinic structure by the XRD. Energy dispersive X-ray spectrum (EDS) confirms the presence of elements in the desired sample. Thermoluminescence (TL) kinetic parameters such as activation energy (E), order of kinetics (b), and frequency factor (s) were calculated by the peak shape method. The orange–red emission was shown to originate from the 5D0–7FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+ ions as the sample was excited at 396 nm. The SrSiO3:Eu3+ phosphor with almost pure orange-red color purity (99.62%) shows the quantum efficiency of 10.2% (excited by 396 nm), which is higher than those of commercial red phosphors Y2O3:Eu3+ and Y2O2S:Eu3+ with quantum efficiencies of 9.6% (excited by 394 nm) and 4.2% (excited by 395 nm), respectively. Mechanoluminescence (ML) intensity of the SrSiO3:Eu3+ phosphor was also found to increase linearly with increasing the impact velocity of the moving piston, suggesting that the discussed phosphor can be used as a stress sensor

Studies on the luminescence properties of CaZrO3:Eu3+ phosphors prepared by the solid state reaction method

CaZrO3:xEu3+ (x = 1.0, 2.0, 3.0, 4.0, and 5.0 mol%) phosphors were successfully prepared by a solid state reaction method. The crystal structure of sintered phosphors was hexagonal phase with space group of Pm-3m. The near ultra-violet (NUV) excitation, emission spectra of the CaZrO3:xEu3+ phosphors were composed of sharp line emission associated with the transitions from the excited states 5D0 to the ground state 7Fj (j = 0, 1, 2, 3, 4) of Eu3+. The results indicated that CaZrO3:xEu3+ might become an important orange-red phosphor candidate for use in white light emitting diodes (WLEDs) with near-UV LED chips. The mechanoluminescence (ML) intensity increases linearly with increasing impact velocity of the moving piston, suggesting that the sintered phosphors can also be useful as a stress sensor

Altering thermal transport by strained-layer epitaxy

Since strain changes the interatomic spacing of matter and alters electron and phonon dispersion, an applied strain can modify the thermal conductivity k of a material. We show how the strain induced by heteroepitaxy is a passive mechanism to change k in a thin film. Molecular dynamics simulations of the deposition and epitaxial growth of ZnTe thin films provide insights into the role of interfacial strain in the conductivity of a deposited film. ZnTe films grow strain-free on latticematched ZnTe substrates, but similar thin films grown on a lattice-mismatched CdTe substrate exhibit 6% biaxial in-plane tensile strain and 7% uniaxial out-of-plane compressive strain. In the T ¼ 700 K–1100 K temperature range, the conductivities of strained ZnTe layers decrease to 60% of their unstrained values. The resulting understanding of dk/dT shows that strain engineering can be used to alter the performance of a thermal rectifier and also provides a framework for enhancing thermoelectric devices