Dy Materials Research Articles

Facile synthesis and thermoluminescence properties of nano bio-ceramic \u03b2-Ca2P2O7:Dy phosphor irradiated with 75\xa0meV C6+ ion beam

Dy3+ doped β-Ca2P2O7 phosphor has been synthesized using wet chemical method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed the formation of β-Ca2P2O7:Dy nano-phosphors. However, photoluminescence (PL) study was carried out to confirm the presence of dopant ion in the host matrix of β-Ca2P2O7:Dy material. Thermoluminescence (TL) glow curves of β-Ca2P2O7 were recorded for different concentrations of Dy3+ after exposure to various fluences of C6+ ion beam (75 meV). TL sensitivity of β-Ca2P2O7:Dy3+ (0.1 mol%) phosphor was 3.79 times more than commercially available CaSO4:Dy3+. TRIM code based on the Monte Carlo simulation was used to calculate the absorbed doses, ion range and main energy loss. Glow curve de-convolution (GCD) method was used to determine the number of TL peaks and their trapping parameters. The wide linear response of β-Ca2P2O7 nanoparticles along with high stability of TL glow curve makes this nanomaterial a good candidate for C6+ ion beam dosimetry.

Thermoluminescence study of gamma irradiated BCNO nanophosphor

Boron carbon oxynitride (BCNO) is a low Zeff (≈6.8), near tissue equivalent material. Nanocrystals of the BCNO:Dy and BCNO:Cu were synthesized by solid state reaction method using different concentrations of dopants. TL characteristics of the synthesized BCNO and BCNO:Dy material doped with 2500ppm concentration of Dy were studied and compared with each other. It is observed that the doping of BCNO with Cu or Dy leads to the quenching of its TL properties. BCNO exhibits a linear response from 1×102 to 2×103Gy whereas BCNO:Dy exhibits a linear response from 1×102 to 1×103Gy of gamma radiations. Fading and reproducibility of phosphors are also studied and it is found that the undoped BCNO shows better TL results than that of Dy doped BCNO phosphor. The main disadvantages of this material are its low thermal stability and high fading, so further studies are needed for this material before concluding it as the best dosimeter for gamma doses.

Thermoluminescence studies of thermally treated CaB4O7:Dy

Abstract Borate based thermoluminescence dosimeters (TLD) show high sensitivity and good TL characteristics. One of the promising material amongst the dosimeters is Dy doped CaB 4 O 7 . Spectrally resolved thermoluminescence of Dy doped CaB 4 O 7 shows three glow peaks at about 50 °C, 240 °C and 380 °C, the intensity of the 240 °C glow peak being the maximum. All TL experiments were conducted on a high sensitivity TL spectrometer at Sussex University with a heating rate of 50 °C min −1 . Two main emissions associated with the Dy dopant are observed at ∼480 and 580 nm. The samples were subjected to a series of treatments including excitation by X-rays and UV laser radiation. As part of the present research CaB 4 O 7 :Dy materials were subjected to two different heat treatments; quenching and slow cooling in order to investigate the changes in TL characteristics.

Magnetothermal study of a Dy-stuffed spin ice:Dy2(DyxTi2−x)O7−x/2

We have studied the thermodynamics of the stuffed spin ice material, ${\text{Dy}}_{2}({\text{Dy}}_{x}{\text{Ti}}_{2\ensuremath{-}x}){\text{O}}_{7\ensuremath{-}x/2}$, in which additional ${\text{Dy}}^{3+}$ replace ${\text{Ti}}^{4+}$ in the pyrochlore ${\text{Dy}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$. Heat capacity measurements indicate that these materials lose the spin ice zero point entropy for $x\ensuremath{\ge}0.3$, sharply contrasting with results on the analogous Ho materials. A finite ac susceptibility is observed as $T\ensuremath{\rightarrow}0$ in both the Ho and Dy materials with $x=0.67$, which suggests that spin fluctuations persist down to $T\ensuremath{\sim}0$. We propose that both the entropy and susceptibility data may be explained as a result of domains of local pyrochlore type structural order in these materials.

On the phosphorescence mechanism in SrAl 2O 4:Eu 2+ and its codoped derivatives

The mechanism of phosphorescence in SrAl 2O 4:Eu,Dy material is discussed on the basis of a thermo-activated release of electrons trapped at oxygen vacancy sites. The depths and concentration of the electron traps are strongly affected by codoping with trivalent lanthanide cations Ln 3+. This finding is rationalized by comparing the ionization potentials of the dopant cation Eu 2+, the codopant cation Ln 3+ and the substituted cation Sr 2+. Such a use of ionization potentials provides a practical guide with which the variation of the phosphorescent decay time in the codoped derivatives of SrAl 2O 4:Eu is predicted.

Crystal structure and magnetic properties of lanthanide- trans-2-butenoate polymers (Ln = La, Pr, Dy, Ho)

Four lanthanide coordination polymers formulated as {[La 3L 9(H 2O) 3]EtOH · H 2O} n 1, {[Pr 2L 6(H 2O) 2]HL · H 2O} n 2, {[Dy 2L 6(H 2O)]0.5HL · H 2O} n 3 and {[Ho 2L 6(H 2O)]0.5HL · H 2O} n 4 and HL = trans-2-butenoic acid have been synthesized from the corresponding pure lanthanide oxide and HL acid in water at pH 3. The compounds were characterized by chemical analysis, IR spectroscopy, thermogravimetry, variable-temperature magnetic susceptibility and single crystal X-ray diffraction studies. A common feature in these materials is the presence of two differentiated lanthanide nodes linked by carboxylates into extended chains. These are further connected by inter- and intra-molecular hydrogen-bonds involving ligand and solvate molecules. Weak ferromagnetic interactions appear to be operative in the Dy material.

Anomalous luminescence in Sr4Al14O25:Eu, Dy phosphors

Sr 4 Al 14 O 25 : Eu , Dy material with an extraordinarily long afterglow was synthesized via a traditional ceramic processing. Such a long afterglow observed can last over 20 h at recognizable intensity level (0.32 mcd/m2), which is attributed to energy exchange between the traps and emission states resulting from Dy and Eu doping. When the Eu2+ concentration doped in the host is less than 1.2 mol %, the emission spectra of Sr4Al14O25:Eu, Dy show two main peaks at 407 and 494 nm, ascribed to two types of Eu2+ centers existing in the Sr4Al14O25 host. The emission peak at 407 nm disappears slowly with increasing concentration of Eu2+ due to the energy exchange between two types of Eu2+ centers.

A New High Sensitive CaSO4 : Dy Thermostimulated Luminescence Phosphor

This paper reports the development of a high sensitive CaSO 4 : Dy thermostimulated luminescence (TLD) phosphor prepared by a new (N) inexpensive technique. Scanning electron microscope photographs reveal that its crystal morphology is quite different from the presently used CaSO 4 : Dy (P). The TSL sensitivity of N (<75 μm) is nearly 60% higher than that of P at low dose levels. Below 1 Gy, the major TSL glow peak of N as well as P occurs at the same temperature (∼230 °C). The 130 °C peak as well as the peaks in the region 300-350 °C are very small in N when compared to those in P. While the glow curve shape of N is nearly invariant with radiation dose up to 10 4 Gy, P exhibits drastic glow curve changes at dose levels ≥ 10 Gy. As a result, the supralinearity of N above 10 Gy is considerably less than that of P. ESR signal in N due to the SO 4 - and SO 3 - radicals related to peak(s) around 130 °C are less intense than those in P. Though the different X-ray diffraction lines of the two powder samples occur at the same d spacings, the relative intensities of almost all the minor lines are considerably reduced in N. The TSL and photoluminescent (PL) emission spectra show the characteristic 480 and 570 nm Dy 3+ lines in both samples but minor changes in their relative intensities between them were noticed. Since the new CaSO 4 : Dy material has better basic TSL characteristics, the new preparation technique (N) is advantageous relative to the presently (P) used one.

Luminescent properties of SrAl 2O 4: Eu, Dy material prepared by the gel method

SrAl 2O 4:Eu,Dy materials were first prepared by the gel method. Compared with samples prepared by solid state reactions, the grain size of the gel method is greatly reduced to nanometer grade. A clear blue shift occurs in the excitation and emission spectra of nano SrAl 2O 4:Eu,Dy, of which the peak of the excitation and emission spectra are at 323 and 500 nm respectively. The brightness of nano SrAl 2O 4:Eu,Dy is greatly reduced. The blue shift and the change of luminescent intensity in nano SrAl 2O 4:Eu,Dy materials can be attributed to the effect of surface energy.

Two- and three-dimensional magnetic order of the rare-earth ions in RBa2Cu4O8.

Neutron scattering has been used to investigate the magnetic ordering of the rare-earth ions in the ${\mathrm{ErBa}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ and ${\mathrm{DyBa}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ materials. For the Er system a simple three-dimensional (3D) antiferromagnetic structure is observed, in which the magnetic unit cell is twice the chemical unit cell along the a axis, with a N\'eel temperature ${\mathit{T}}_{\mathit{N}}$\ensuremath{\approxeq}0.49 K. In the vicinity of the N\'eel temperature, however, scattering characteristic of two-dimensional behavior, indicative of the strong anisotropy of the magnetic interactions, is observed. The magnetic anisotropy arises naturally from the crystal structure, as the c-axis spacing of the magnetic ions is \ensuremath{\sim}3 times the a-b spacing. 2D behavior is also observed in the Dy material near its N\'eel temperature of \ensuremath{\sim}0.9 K. However, the scattering in the Dy system does not cross over to the expected 3D Bragg peaks at low temperatures, but rather the 2D line shape persists to the lowest temperatures measured. We explain this result as originating from a geometric cancellation of interactions between c-axis layers for the specific Dy a-b spin configuration, which together with the weak intrinsic c-axis interaction renders the net interaction along the c axis much smaller than all other known ``2D magnets.'' Hence the 2D and 3D ordering temperatures appear to be quite different for the Dy material. We anticipate that a similar cancellation of interactions is likely to occur in other R${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ (R being a rare-earth element) systems.