Function Of Nd Concentration Research Articles

Deciphering the Nd3+ environment and energy-transfer mechanisms in thermally stable novel calcium aluminate glasses: elucidation of broadband high-gain performance for laser applications

Rare-earth-doped barium calcium aluminate (BCA) glasses, having extended infrared (IR) transmission (6 μm), are attractive materials for near IR (NIR) photonic applications. Nd2O3-doped BCA glasses display broadband emission at 1.07 µm, but they are limited, with poor glass-forming ability (GFA) and low emission cross sections. In the present study, four different barium zinc calcium aluminate (BZCA) glasses are synthesized with varied ZnO concentrations (from 9.5 to 24.5 mol%) and doped with 0.5 mol% Nd2O3 to decipher the effect on GFA and spectroscopic properties. The addition of ZnO enhances the GFA, and the NdBZCA20 glass shows the maximum GFA. Ultraviolet (UV)–visible (Vis)–NIR absorption spectra reveal a decreasing trend in the nephelauxetic effect, while J–O parameters, emission, and gain properties lead to no significant alteration with increasing ZnO, and the structure–properties correlation is established accordingly. However, the emission cross sections for all ZnO concentrations are found ∼4.5 × 10−20 cm2 accompanied by broadband emission (Δλ eff ∼ 40 nm), which ensures the potentiality of these glasses for low-threshold high-gain laser applications as well as ultrashort pulse laser applications. Furthermore, a thorough analysis of 1.06 µm emission as a function of Nd concentration in the BZCA20 glass is reported here. The emission spectra and decay time indicate that 0.5 mol% is the optimized doping concentration. Inokuti–Hirayama and Burshtein equations are adopted to study the decay kinetics and energy-transfer mechanisms, which confirm that the energy-transfer process due to cross-relaxation is dominant up to 0.5 mol% concentration, whereas, beyond that concentration, excitation energy migration via the hopping mechanism supersedes.

Poly (vinyl alcohol)/nano-diamond composite films and hydrogels prepared by gamma ray

Abstract Poly (vinyl alcohol) and nano-diamond, PVA/ND, hydrogels were prepared and assessed as prosthetic material suitable for replacement of the nucleus pulposus. The hydrogels were prepared by gamma irradiation at various doses (15 kGy, 25 kGy, 35 kGy, 45 kGy) and at various ND concentrations ranging from 0.25 wt.% to 3 wt.%. Extent of gelation, equilibrium water content, and viscoelastic properties of swelled hydrogels at definite water contents were measured and examined as a function of ND concentration as well as gamma dose. According to viscoelastic measurements, the strength of hydrogels increased considerably over that of pure PVA at a low concentration of ND. By increasing irradiation dose, gel percent and strength of hydrogels increased. Hydrogel water content was in a range of 80 wt.% to 90 wt.% similar to that of natural nucleus pulposus. The G″ values of hydrogels were much smaller than G′ values indicating elastic behavior. Also PVA/ND nanocomposite films were prepared at various ND concentrations by solution casting. The ND particles were uniformly distributed within PVA films. Tensile modulus and strength of the films increased over pure PVA.

Temperature dependent, large electromechanical strain in Nd-doped BiFeO3-BaTiO3 lead-free ceramics

Lead-free piezoceramics with the composition 0.7(Bi1-xNdx)FeO3-0.3BaTiO3+0.1wt% MnO2 (BNxF-BT) were prepared using a conventional solid state route. X-ray diffraction and temperature dependent permittivity measurements indicated a transition from a composition lying at a morphotropic phase boundary (MPB) to a pseudocubic phase as a function of Nd concentration. The highest maximum strain (Smax∼0.2% at 60kV/cm) and effective piezoelectric coefficient (d33*=333 pm/V) were obtained at room temperature for the composition BN0.02F-BT. The decrease in remanent polarization (Pr) and Berlincourt d33 with increase in Nd concentration can be attributed to the coexistence of ferroelectric and relaxor phases. In-situ polarisation and strain measurements revealed an increase in Pr and d33* with temperature and a reduction in the coercive field EC. Presumably this behavior is due to a combination of thermally activated domain wall motion and lowering of the activation energy for a field induced relaxor-ferroelectric transition, as the Curie maximum is approached.

A first principles study of Nd doped cubic LaAlO3 perovskite: mBJ+U study

The structural, electronic and magnetic properties of Nd-doped Rare earth aluminate, La1−xNdxAlO3 (x=0–100%) are studied using the full potential linearized augmented plane-wave (FP-LAPW) method within the density functional theory. The effects of Nd substitution in LaAlO3 are studied using super-cell calculations. The electronic structures were computed using modified Beck Johnson (mBJ) potential based approximation with the inclusion of Coulomb energy (U) for Nd-4f state electrons. The La1−xNdxAlO3 may possess half metallic behavior on Nd doping with finite density of states at EF. The direct and indirect band gaps were studied as a function of Nd concentration in LaAlO3. The calculated magnetic moments in La1−xNdxAlO3 were found to arise mainly from the Nd-4f state electrons. A probable half-metallic nature is suggested for these systems with supportive integral magnetic moments and high spin polarized electronic structures in these doped cases at EF. The controlled decrease in band gap with increase in concentration of Nd doping is a suitable technique for harnessing useful spintronic and magnetic devices.

Structural phase transitions in Ti-doped Bi1-xNdxFeO3 ceramics

Recently, it was demonstrated that donor doping with Ti on the B-site significantly reduces the conductivity in Bi0.85Nd0.15FeO3 ceramics [Kalantari et al., Adv. Funct. Mater. 21, 3737 (2011)]. In this contribution, the phase transitions as a function of Nd concentration are investigated in 3% Ti doped Bi1-xNdxFeO3 ceramics. Paraelectric (PE) to ferroelectric (FE) transitions were observed for compositions with x ≤ 0.125 which manifested themselves as peaks in permittivity. In contrast, PE to antiferroelectric (AFE) transitions for 0.15 ≤ x ≤ 0.20 gave rise to a step-like change in the permittivity with x = 0.25 exhibiting no sharp anomalies and remaining PE until room temperature. The large volume change at the PE to FE/AFE transitions, reported by Levin and co-workers [Phys. Rev. B 81, 020103 (2011)] and observed here by dilatometry, coupled with their first-order character constrain the transitions to occur uniformly throughout the material in an avalanche-like manner. Hence, the anomalies in DSC, permittivity and thermal expansion occur over a commensurately narrow temperature interval. However, despite the large volume change and eye-catching anomalies in DSC, the latent heats for the transitions in Ti-doped Bi1-xNdxFeO3 are similar to Pb(Zr,Ti)O3 (1–3 kJ/mol) with each an order of magnitude greater than BaTiO3 (∼0.2 kJ/mol). A broad frequency dependent dielectric anomaly of unknown origin in the temperature range 250–450 °C was also observed in all samples.

Fluorescence dynamics and laser properties of the Nd 3+ : Ca 3Ga 2Ge 3O 12 crystal

Spectral and dynamical changes in the fluorescence of Nd 3+ in the Ca 3Ga 2Ge 3O 12 garnet have been investigated as a function of Nd concentration. These experimental results are then used to interpret the increase observed in the laser threshold with the Nd content.

Systematics of the physical properties of compounds

A study of systematics was carried out on compounds by replacing Ca with Nd ions. The dependence of on structural parameters, oxygen content and hole carrier concentration was observed as a function of Nd concentration. X-ray diffraction patterns show the single phase (2212) nature of the samples. Lattice parameters have been calculated and the results show an increase in a-axis with a simultaneous decrease in c-axis. Oxygen content was estimated from the iodometric titration method and was shown to increase with x. The measured (0) and (onset) obtained from resistivity and susceptibility data were found to decrease with increasing Nd concentration. Vacuum annealing was found to improve . The materials exhibited superconductivity in the concentration range, and for higher concentrations of Nd they became semiconducting. In the semiconducting region, the conduction was found to be due to the 3D variable range hopping (VRH) mechanism. The initial susceptibility dM/dH relating to the superconducting volume, has shown a continuous decrease with increasing Nd concentration. The hole carrier concentration was computed from thermoelectric power data and found to decrease with increasing Nd ion concentration. The results are presented and discussed in comparison with those obtained from system.

Site-selective spectroscopy of Nd3+ in the Ca3Ga2Ge3O12 laser crystal

Laser excited site-selection spectroscopy of Nd 3+ ion in the Ca 3 Ga 2 Ge 3 O 12 laser garnet crystal has been investigated for the transitions Z 1 (I 9/2 )→D 1 ( 4 G 5/2 ) and 4 F 3/2 → 4 I 9/2 in order to understand the nature of the different Nd centers in terms of the possible charge compensating defects. Lifetime data of the 4 F 3/2 → 4 I 9/2 transition obtained as a function of Nd concentration have allowed to distinguish the Nd 2+ ions compensated by Ga 3+ ions (Nd 3+ (Ca 2+ )-Ga 3+ (Ge 4+ )) from other kind Nd 3+ ions, which can be presumably associated with Nd 3+ (Ca 2+ )-Nd 3+ (Ge 4+ ) pairs

Magnetic properties and crystallization of the rapidly quenched (Fe 1- x Nd x ) 81.5 B 18.5 alloys

Magnetic properties and crystallization behaviors of amorphous (Fe1-xNdx)81.5B18.5 alloys were studied. The crystallization temperature is found to rise at first and then drop monotonically with x, having a maximum value of 976 K at x = 0.11 (9 at% Nd). The (Fe1-xNdx)81.5B18.5 alloys prepared at a quenching rate of vs = 6.6 m/s are amorphous, and exhibit good glass formability. Both the coercive field Hc and energy product (BH)max depend strongly on Nd concentration. Amorphous (Fe1-xNdx)81.5B18.5 alloys with higher Nd concentration have a high coercive field at low temperature, due to the large random uniaxial anisotropy of Nd. The room-temperature Hc and (BH)max obtained on optimal annealing conditions show two maxima as a function of Nd concentration x. The highest room-temperature coercive field Hc = 22 kOe within the Nd concentrations around x = 0.368 and the maximum energy product (BH)max = 13.3 MG Oe at x = 0.055 are observed. The hard magnetic properties of these crystallized samples are related to the presence of the hard magnetic Nd2Fe14B phase.

Concentration quenching inNdxY1−xP5O14crystals

An extensive investigation of the spectroscopic properties of ${\mathrm{Nd}}_{x}{\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{P}}_{5}{\mathrm{O}}_{14}$ is reported. Time-resolved site-selection spectroscopy and photoacoustic spectroscopy techniques were used as well as standard optical spectroscopy measurements which were made as a function of Nd concentration, temperature, excitation wavelength, and laser power. Results show that Nd ions occupy a variety of slightly perturbed sites. No significant energy transfer appears to be taking place between ions in these inequivalent sites. Additional experimental data presented here suggest a new quenching model for neodymium pentaphosphate crystals based on spatial but nonspectral energy migration to surface quenching sites.