Single crystal of tri glycine sulphate has been grown in the presence and absence of l-glutamic acid and sodium sulphate by slow evaporation growth. The grown crystal was analyzed by single crystal ...X-ray diffraction. FTIR studies were used to confirm the presence of functional groups present in the grown crystals. The optical absorbance studies show the cut off wavelength to be 235 nm. The phase transition temperature was found to be 50 degree C from DSC analysis. The dielectric behavior was identified. The AC conductance of the grown crystal was plotted. PE loop measurement is taken.
The Sr1.99-xBi0.01CeO4:xRE3+ (RE3+ = Dy3+, Sm3+ and Eu3+, x = 0 and 0.03) single, co-doped and tri-doped phosphors synthesized by solid state reaction technique and their structure analysed by X-ray ...powder diffraction technique (XRD). The results shows that the Dy3+,Sm3+, Eu3+, Dy3+/Sm3+, Sm3+/Eu3+, Dy3+/Eu3+, and Dy3+/Sm3+/Eu3+ ions are effectively studded into the host lattice site without changing the structure of the host. The luminescence and energy transfer properties of the Sr1.99-xBi0.01CeO4:xRE3+ have been investigated for single, co-doped and tri-doped phosphors under each of the 387 nm (Dy3+: 6H15/2 → 4I13/2), 409 nm (Sm3+: 6H5/2 → 6P3/2) and 466 nm (Eu3+: 7F0→5L6) excitation levels wherein the mean emission values reportedly seem to be 572, 651 and 615 nm respectively. The chromaticity coordinates and decay time of the synthesized materials are also examined.
•Effect of single, co- and tri-dope RE3+ ion in SBC host.•Obey the rule of the Kroger-Vink defect.•Analyzing the energy transfer mechanism.
Pure and thiourea (5 mol%) doped potassium dihydrogen orthophosphate (KDP) single crystals were grown by solution growth method using slow evaporation technique and its ferroelectric properties were ...analyzed. The KDP and their doped crystals display ferroelectric behavior at ambient temperature, followed by a phase transition from ferroelectric to ferroelectric second-order phase transition and better ferroelectric activity as temperature increases and show no polarization loss after 1200 frequency cycles, as proven by fatigue studies. Remarkable ferroelectric property has been observed in single crystals of KDP and its dopant at room temperature, despite having a Curie point at low temperatures.
The KTiOPO4:Yb (KTP:Yb) crystal has been grown by flux growth at high temperature (~1243−1223K ). KTP:Yb crystallizes in the orthorhombic crystal system with Pna21 space group. Ytterbium presence was ...analyzed in the grown crystal by EDAX analysis. The existence of Ti3+ color center has been evaluated using electron paramagnetic spin resonance spectrum. The Raman spectroscopic techniques were used to study the effect of Yb3+ in KTP crystal. Thermal diffusivity, thermal conductivity and specific heat capacity of grown crystal were studied. At low frequency, the dielectric constant decreases sharply in the frequency region of 104Hz. The electrical conductivity along the 001 is low (9.0435×10−7S/cm) for 60kHz at 300K. The temperature dependent variation of electric conductivity was found for 010 and 001 of KTP:Yb. The effect of Yb3+ doping in second harmonic generation of KTP was studied.
•The transparent KTP:Yb crystal were grown by the TSSG technique.•The weak EPR signal is attributed to the less Ti3+ center in KTP:Yb.•Low ionic conductivity of 9.0435×10−7S/cm was observed for Yb3+ doped KTP.
•Ferroelectric property in pyrochlore Tb2Ti2O7 is confirmed from polarisation versus electric field above 382 K.•The dielectric and magnetic measurements also show an anomaly around 383 K evincing ...the observed ferroelectric property.•The possible mechanism for the ferroelectric property in this compound is discussed.
We report the ferroelectric property in Tb2Ti2O7 pyrochlore, prepared by a two-step solid-state reaction method. A concave P-E (polarisation vs electric field) loop observed from 382 K confirms ferroelectricity, below which the loop remains as pointed or banana-shaped. Dielectric plots clearly show an anomaly at 383 K and the magnetic data reveals a deviation from 380 K supporting the observed ferroelectric ordering. The origin of ferroelectricity in Tb2Ti2O7 is discussed which is due to the structural distortion in TiO6 octahedron.
The Sr.sub.1.95Ba.sub.0.05 CeO.sub.4:Eu.sup.3+ phosphors are synthesized by the solid-state reaction method. The samples are characterized using X-ray diffraction (XRD), diffuse reflectance ...spectroscopy and photoluminescence (PL) spectra. The XRD results reveal that the synthesized phosphors are genuine crystalline and belong to the orthorhombic structure. The intense PL emission is optimized from the PL spectra at various doping concentrations of europium ions. The results indicates that the phosphor can be effectively excited under 264 nm wavelength producing on intense emission spectrum of the synthesis material at 484 nm (blue region). The color purity of the phosphor is confirmed by CIE coordinates (x = 0.217, y = 0.265). The experimental data indicate that the prepared phosphors can be used as blue-emitting material in the field of illuminations and display devices.
Sensitized luminescence properties of various alkali halide single crystals of dosimetric importance doped with aliovalent impurities are studied. Single crystals of KCl co-doped with (Ce,Mn), ...(Ce,Mg) (Ce,Tb) and (Eu,Tb) are grown using the Czochralski technique. The XRD of grown crystals showed good crystalline nature with face-centred cubic KCl structure. Thermally stimulated luminescence (TSL) and optically stimulated luminescence (OSL) characteristics of grown crystals are investigated after subjecting to gamma dose. TSL response of KCl:Eu,Tb and KCl:Ce,Tb showed an enhancement of 6.5 times and 3.5 times, respectively, compared to singly doped KCl:Tb. Co-doping of the divalent activators such as Mn and Mg did not result in enhanced TSL response with rare earth sensitizers. Notwithstanding the low TSL response, KCl:Ce,Mn showed very high OSL response, six times than that of single-doped KCl:Tb and 3.5 times than that of KCl:Ce,Tb and KCl:Eu,Tb. However, KCl:Ce,Mg did not exhibit noticeable OSL intensity enhancement compared to single doping. The high TSL and OSL response is apparently the conclusive evidence of the energy transfer mechanism between dopants, which is confirmed by photoluminescence studies. The dose–response curve of KCl:Ce,Mn that exhibited very high OSL response showed linearity up to 100 Gy, which indicated the material is a good candidate for dosimetric applications. The growth and characterisation of aliovalent impurity-doped KCl single crystals and mechanism of resonance energy transfer between the dopants are discussed in this paper.
Near-infrared emitting phosphors of ytterbium doped titania are synthesized by precipitation method using titanium tetrachloride as a raw material. X-ray diffraction technique is to analyze the ...structure, ultraviolet-visible diffuse reflectance spectroscopy to determine the band gap energy and photoluminescence spectroscopy to characterize the luminescence properties of the synthesis material. The HRSEM and HRTEM are used to measure the morphology structure of the sample. This sample is excited by ultraviolet irradiation, exhibits an intense band emission near NIR region between super(2)F sub(5/2) and super(2)F sub(7/2) transition of Yb super(3+) ions using photoluminescence spectroscopy. The observation discusses the possible energy transfer mechanism between TiO sub(2) and Yb super(3+) ions. The results determine the synthesized material is adept for silicon based solar cells.
•3-Hydroxy-4-methoxybenzaldehyde single crystal was grown by vertical Bridgman method.•Single wall ampoule bottom with and without cone angle is used for the experiment.•Structural,Optical, thermal ...and electrical properties have been studied.
An organic nonlinear optical material 3-Hydroxy-4-methoxy benzaldehyde (3H4MB), also named as isovanillin, was grown using the vertical Bridgman crystal growth technique. The crystalline perfection and lattice parameters of the grown crystal were calculated using single-crystal and powder X-ray Diffraction (XRD) analysis. The thermogravimetric/ differential thermal analysis (TG/DTA) and differential scanning calorimetry (DSC) are used to measure the 3H4MB thermal stability. The NMR spectral analysis confirmed the molecular structure of the grown crystals. The 3H4MB single crystal is optically transparent at the region of 360 to 1100 nm with the bandgap of 3.45 eV. The dielectric constant and loss were measured in the frequency range of 50 Hz to 5 MHz. The obtained results confirm that the 3H4MB single crystal is suitable for opto-electrical applications.
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