Ions In Octahedral Symmetry Research Articles

New fuel governed combustion synthesis and improved luminescence in nanocrystalline Cr3+ doped ZnAl2O4 particles

This paper describes the solution combustion (SCS) synthesis of nanocrystalline Cr3+ doped ZnAl2O4 (ZAC) particles using a new efficient fuel. A thorough investigation was conducted to comprehend the interaction of dopant (Cr3+) and ZnAl2O4 host matrix, as well as the influence of doping on their structural, optical, and luminescence characteristic properties. The powder samples were thoroughly characterized using XRD, UV–Visible Diffuse Reflectance, and Photoluminescence spectroscopic techniques. The XRD analysis demonstrates the formation of polycrystalline nanoparticles, as well as a decrease in crystallite size with increasing Cr3+ concentration. The band gap energy red-shifted as Cr3+ was incorporated into the host matrix. The diffuse reflectance spectra show two absorption peaks at 395 nm and 540 nm are assigned to the 4A2g →4T1g and 4A2g →4T2g characteristic transitions of Cr3+ ions. The PL emission spectrum, on the other hand, shows four distinct peaks, indicating the manifestation of Cr3+ ions in octahedral symmetry, that is, Cr3+ ions in a strong crystal field. Increases in Cr3+ concentration result in luminescence enhancement up to x = 0.07 and suppression of luminescence observed beyond that concentration. In addition, the dopant ion's Racah parameters, crystal field parameters, and local site symmetry are calculated.

STRUCTURAL, OPTICAL, AND PARAMAGNETIC INVESTIGATIONS OF (Mn2+) IONS DOPED ZINCALUMINOBOROPHOSPHATE (ZnAlBP) GLASS SYSTEM

Concentration variation of Mn2+ ions doped zincaluminoborophosphate (ZnAlBP) glasses of 40 ZnO + 25 H3BO3 + (30-x) P2O5 + 5 Al2O3 + x MnO with 0  x  0.8 (x=0, 0.2, 0.4, 0.6 and 0.8) have been prepared and investigated by structural and spectroscopic techniques. The XRD diffractograms confirm the amorphous nature of the prepared samples. The FTIR spectra reveal the existence of BO3 and BO4 units along with fundamental P-O-H and B-O-H structural units in the present glass system. The Optical absorption spectra exhibit two low intensity bands centered at 407 nm (24,570 cm-1) and 689 (14,514 cm-1). These bands were assigned to 6A1g(S) → 4A1g (G) + 4Eg (G) and6A1g(S) → 4T1g (G) characteristic transitions of Mn2+ ions in octahedral symmetry. Tauc’s plots were drawn to measure the optical band gaps for the direct and indirect transitions. The energy gaps show a decreasing trend for the selected ZnAlBP: Mn2+ glass system. The well-resolved hyperfine splitting EPR spectra of prepared glass samples exhibit resonance at g ≈ 1.98 indicating the Mn2+ ions are in octahedral site symmetry. The hyperfine splitting factor (hfs), the number of spin levels (N), hyperfine constant (A), zero-field splitting parameter (D), and paramagnetic susceptibility (χ) have been determined. The magnitude of g indicates the predominant ionicity in the glasses.

Nickel(II) Metal Complexes as Optically Addressable Qubit Candidates

The inherent atomic level structural control of synthetic chemistry enables the creation of qubits, the base units of a quantum information science system, designed for a target application. For quantum sensing applications, enabling optical read-out of spin in tunable molecular systems, akin to defect-based systems, would be transformative. This approach would bring together molecular tunability with optical read-out technology. In theory, nickel ions in octahedral symmetry meet all the criteria for optical readout of spin. Yet, to the best of our knowledge, there are no pulse EPR studies on Ni2+ molecules. We identified two compounds featuring highly symmetric Ni2+ centers, thereby engendering weak zero-field splitting to enable EPR addressability: [Ni(phen)3](BF4)2 (1) and [Ni(pyr3)2](BF4)2 (2) (phen = 1,10-phenanthroline; pyr3 = tris-2-pyridyl-methane). Crucially, these complexes feature the requisite strong field ligands to enable emission for optical addressability. We extracted axial zero-field splitting parameters of D = +0.9 cm-1 and +2.7 cm-1 for 1 and 2, respectively, enabling pulse EPR measurements. Both compounds produce emission at λmax = 938-944 nm. The aggregate of these results expands the catalogue of qubit materials to Ni2+-based compounds and offers a future pathway for optical readout of these molecules.

Spectroscopic properties of alkali alkaline earth borate glasses doped with Fe3+ ions

Iron oxide–doped lithium calcium borate glasses with composition (in mol%) of 25Li2O–15CaO–(60-x) B2O3: xFe2O3 (0 ≤ x ≤ 1) (LCBF) have been synthesized by melting and quenching technique. The physical and spectroscopic properties were accomplished using XRD, density, UV-Visible, EPR, FTIR and Raman spectroscopic techniques. XRD patterns have not revealed any crystalline peaks indicating the non-crystalline or amorphous characteristic of the glass samples. The density of the studied glasses increased with increasing iron ion concentration from 0 to 0.8 mol% (insteps of 0.2 mol%), and further, it is found to decrease. This may be due to the metamorphosis transformation of some tetrahedral Fe3+ (Th) to octahedral Fe3+ (Oh). The refractive index shows small variation with the iron ion concentration. In optical absorption spectra, only one absorption band exists at around 452 nm analogous to the 6A1g (S) → 4A1g (G); 4Eg (G) transition and is a peculiarity of iron ions in octahedral symmetry. The absorption edge shifts towards the greater wavelength with enhancing Fe3+ ion concentration. The optical band gap energy (Eopt) and Urbach energy (ΔE) are deliberated from their UV absorption edges. The EPR spectra exhibit three resonance signals at g ≈ 8.033, 4.282 and 2.0032. The resonance signal at g ≈ 8.033 is imputed to Fe3+ ions at axial symmetry sites whereas the resonance signal at g ≈ 4.282 is ascribed to isolated Fe3+ ions at rhombic symmetry site. The resonance signal at g ≈ 2.0032 is attributed to Fe3+ ions coupled by exchange interaction. The FTIR and Raman spectral studies divulge that iron ions accompanied to structural changes through the conversation of BO3 into BO4 and thereby diminishing the number of non-bridging atoms. The non-linear variations of several structural and optical properties portray a brawny structural consequence of iron ions on the LCB glass system.

Spectroscopic, thermal, structural and electrical studies on VO2+ ions doped PVA/MAA:EA polymer blend films

Abstract Pure and VO2+ ions doped PVA/MAA:EA polymer blend films were prepared by a solution casting method. XRD pattern reveals an increase in amorphicity with increase in doping. The dTGA study shows an enhancement of thermal stability of the system with increase in dopant concentration. The optical absorption spectrum exhibits three bands corresponding to the transitions 2B2g→2A1g, 2B2g→2B1g and 2B2g→2Eg, characteristic of VO2+ ions in octahedral symmetry with tetragonal distortion and reflects that the optical band gap decreases with the increase of mol% of VO2+. EPR spectra of all the doped samples show a characteristic eightline hyperfine structure of VO2+ ions, which arises due to the interaction of unpaired electron with the 51V nucleus. The spin-Hamiltonian parameters (g and A) evaluated from the EPR spectra confirm that the vanadyl ions exist as VO2+ ions in octahedral co-ordination with a tetragonal compression and have a C4v symmetry. The impedance spectroscopic study shows that the addition of VO2+ ions into the polymer blend system enhances the ionic conductivity which is explained in terms of an increase in the amorphicity.

1s2p RIXS Calculations for 3d Transition Metal Ions in Octahedral Symmetry

We present a series of 1s2p resonant inelastic X-ray scattering (RIXS) calculations for 3d transition metal ions in octahedral symmetry covering each ground state between 3d0 and 3d9. The calculations are performed in octahedral (Oh) symmetry using the crystal field multiplet theory. We discuss the crystal field effects and the selection rules with respect to the 1s2p RIXS pre-edge and compare their final state energies with the corresponding 2p X-ray absorption spectrum (XAS). The calculations provide a detailed understanding of 1s2p RIXS and serve as a basis for the future analysis of experimental spectra and also as a starting point for calculations that add additional channels including the nonlocal peaks.

Effect of alkaline earth modifier on the optical and structural properties of Cu2+ doped phosphate glasses as a bandpass filter

Glasses of composition [16RO–3Al2O36CuO20Na2O55P2O5], where R is the alkaline earth (R = Mg, Ca, Sr and Ba mol. %), were prepared by conventional melt quenching technique. The glass samples were characterized by X-ray diffraction, infrared spectroscopy, and spectrophotometer. XRD patterns show no sharp peaks indicating the non-crystalline nature of the prepared glasses. The density and molar volume of the glass systems were determined in order to study their structures. These results revealed that addition of alkaline earth elements leads to the formation of non-bridging oxygens (NBOs) and expands (opens up) the structure. The infrared spectra were analyzed to quantify the present phosphate groups. The optical absorption spectra of Cu2+ ions show the characteristic broadband single of Cu2+ ions in octahedral symmetry. The band gap was estimated following two methodologies. The first method considers the band edge of the transmission, while the second approach relays on the estimated values of the optical constants. A decent agreement for the band gap values using the two methods was obtained.

Photoluminescence properties of broadband deep-red-emitting Na2MgAl10O17:Mn4+ phosphor

A new non-rare-earth deep-red-emitting Na2MgAl10O17:Mn4+ phosphor is prepared successfully by high temperature solid-state reaction method in air. All samples are a single pure phase, which is confirmed by X-ray powder diffractions patterns. Excitation spectrum shows some absorption bands in the range of 220–600 nm, which are line with the wavelength of ultraviolet (UV), near UV, and blue light-emitting diode chips. Deep-red emission of Na2MgAl10O17:Mn4+ phosphor with excitation UV, near UV, and blue light can be observed in the range of 600–810 nm due to the 2E → 4A2 transition of Mn4+ ion in octahedral symmetry with aided the lattice vibration. The full width at half maximum (FWHM) is ∼105 nm. The optimal Mn4+ concentration is ∼1%. Decay curve and time-resolved spectra indicate that there is only a Mn4+ ion luminescent center in Na2MgAl10O17:Mn4+ phosphor. The thermal stability is investigated and analyzed by the configuration coordinate diagram of Mn4+ ion.

Gamma Ray Irradiation Effects on the Mechanical and Chemical Properties of CuO–Bi<sub>2</sub>O<sub>3</sub>–SiO<sub>2</sub> Glasses

The effect of gamma radiation on the mechanical and chemical properties of x CuO, (70-x) Bi₂O</sub>3<sub>, 20SiO₂,10 Na₂O, where 0 ≤ x ≤ 30 weight % were carefully studied in order to obtain information about the changes that appear in the structure of the glass matrix with the doping of copper ions. The glass matrix was fabricated by melt-quenching technique. The results showed that, the glass system has good durability, density and mechanical properties with increasing CuO content at the expense of Bi₂O₃, and that the effect of irradiation with gamma dose is very small. UV-VIS absorption spectra for all glasses have a single asymmetric band, which corresponds to a BiO₃→BiO₆ transition of the Cu²⁺ ions in octahedral symmetry with an elongated tetragonal distortion. These measurements indicate the presence of Cu²⁺ ions in the glasses. Furthermore, it has good water resistance ability with increasing copper oxide. So, it can be used as a container for keeping radioactive waste and radioactive sources.

Theoretical explanation of optical absorption spectra for nickel ion at the interstitial site of zinc borate nanopowder

ABSTRACTZinc borates have been used in a variety of applications, including cellulose fibers, textiles, optical materials, and intumescent systems. They have also received many experimental investigations, including metallic ions doping. However, the relevant theoretical studies are absent, especially for the optical spectra and microstructures of zinc borates contained metallic impurities. In this work, as a typical example, the absorption spectra for nickel ions at the interstitial sites in the zinc borate nanopowders are theoretically investigated from the complete energy matrix method based on the two-spin–orbit parameter model and the suggested local defect model for nickel ion in octahedral symmetry. The theoretical results are in good agreement with the experimental values. The local lattice distortion induced by the impurity nickel at the interstitial site of zinc borate nanopowder is also estimated from the calculations. These results are discussed.

Optical, magnetic and electrical properties of multifunctional Cr3+: Polyethylene oxide (PEO) + polyvinylpyrrolidone (PVP) polymer composites

Multifunctional polymer composite films of PEO + PVP and also doped with Cr3+ ions in different concentrations have been synthesized by a solution casting method. The semi-crystalline nature of the polymer films was confirmed by XRD studies. Raman spectral analysis confirms the complex formation of the polymer with dopant ions. The optical absorption spectrum of Cr3+ doped polymer exhibits three absorption bands pertaining to Cr3+ ions in octahedral symmetry. From the absorption spectrum, Racah parameters were evaluated. The red emission at 614 nm (4T2g→4A2g) has been observed for the Cr3+: PEO + PVP polymer under the UV excitation. EPR spectra of Cr3+ ions doped polymers at different concentrations of Cr3+ ions exhibit resonance signals which are characteristic of Cr3+ ions in the octahedral symmetry. Cr3+: PEO + PVP revealed the superparamagnetic nature based on the trends on Vibrational Sample Magnetometer profiles. Cr3+(0.1 wt%): PEO + PVP polymer reveals high ionic conductivity in the order of 1.14 × 10−5 S/cm at 373 K. Dielectric constant behaviour has also been analysed with respect to frequency.

Physical and Optical Properties of Calcium Zinc Borophosphate Glasses Doped with Manganese Ions

This article reports on the physical and optical properties, absorption, and luminescence spectra in the visible region, of calcium zinc borophosphate glasses doped with manganese ions. The manganese composition was varied up to 10 mol%. The aim of this work was to investigate the effect of the luminescence properties when the glasses were doped with different compositions of manganese ions. X-ray diffraction profiles confirmed their glassy nature. The optical absorption spectrum showed bands characteristic of manganese ions in octahedral symmetry. Both excitation and emission spectra were recorded for these glasses to understand their optical performances. The emission spectrum showed a single broad band (green region) in octahedral symmetry at 582 nm as a result of transition from the upper 4T1g state to the 6A1g ground state of manganese ions. As the concentration of manganese ions increased, the emission band increased from 582 nm (green-light emission) to 650 nm (red-light emission). Apart from the spectral analysis, different physical properties of these glasses were also analyzed. Based on the physical and optical properties, we found the samples to be more promising for their use as novel luminescent optical materials.

Structural and optical investigations of VO(II) ions doped NaCaAlPO4F3 phosphor

VO(II) ions doped NaCaAlPO4F3 phosphor have been synthesized by solid state reaction. The prepared sample was characterized by powder X-ray diffraction (P-XRD), Optical absorption, Photoluminescence (PL), Electron Paramagnetic Resonance (EPR) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. From powder XRD data the average crystallite size and structural parameters are evaluated. The morphology of prepared sample was examined by Scanning Electron Microscope (SEM) images at different magnifications. Optical absorption spectrum showed characteristic bands corresponding to d–d transitions of VO(II) ions. EPR spectrum of prepared sample exhibited resonance signal characteristic of VO(II) ions in octahedral symmetry with tetragonal compression having C4V symmetry. The spin-Hamiltonian parameters (g and A), dipolar hyperfine coupling parameter (P) and Fermi contact interaction parameter (κ) have been evaluated. From the optical and EPR data, various molecular coefficients are evaluated, and the nature of bonding with ligands is covalent. PL spectrum exhibited visible emission at green, yellow and red regions under 420 nm photon excitation. The calculated Commission Internationale de l’Eclairage (CIE) coordinates are in yellowish green region at (0.382, 0.509). The prepared material is suitable for display devices. FT-IR spectrum marked the characteristic vibration bands of prepared phosphor material.

EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

Antimony phosphate glasses (SbPO) doped with 3 and 6mol% of Cr3+ were studied by Electron Paramagnetic Resonance (EPR), UV–VIS optical absorption and luminescence spectroscopy. The EPR spectra of Cr3+-doped glasses showed two principal resonance signals with effective g values at g=5.11 and g=1.97. UV–VIS optical absorption spectra of SbPO:Cr3+ presented four characteristics bands at 457, 641, 675, and 705nm related to the transitions from 4A2(F) to 4T1(F), 4T2(F), 2T1(G), and 2E(G), respectively, of Cr3+ ions in octahedral symmetry. Optical absorption spectra of SbPO:Cr3+ allowed evaluating the crystalline field Dq, Racah parameters (B and C) and Dq/B. The calculated value of Dq/B=2.48 indicates that Cr3+ ions in SbPO glasses are in strong ligand field sites. The optical band gap for SbPO and SbPO:Cr3+ were evaluated from the UV optical absorption edges. Luminescence measurements of pure and Cr3+-doped glasses excited with 350nm revealed weak emission bands from 400 to 600nm due to the 3P1→1S0 electronic transition from Sb3+ ions. Cr3+-doped glasses excited with 415nm presented Cr3+ characteristic luminescence spectra composed by two broad bands, one band centered at 645nm (2E→4A2) and another intense band from 700 to 850nm (4T2→4A2).

EPR and optical investigations of LaMgAl11O19:Cr3+ phosphor

The LaMgAl11O19:Cr3+ phosphor has been prepared by a low-temperature combustion synthesis method. As-prepared combustion synthesized powder was characterized using powder X-ray diffraction (XRD), diffuse reflectance (DRS), electron paramagnetic resonance (EPR) and photoluminescence (PL) studies. The X-ray diffraction pattern reveals crystalline hexagonal phases. The UV–vis diffuse reflectance spectrum exhibits three broad bands characteristic of Cr3+ ions in octahedral symmetry. The EPR spectrum exhibits several resonance signals. The signals with the effective g values at g=4.84, 3.64 and 2.26 have been attributed to the isolated Cr3+ ions. The signal with the effective g value at g=1.94 has been attributed to exchange coupled Cr3+–Cr3+ ion pairs. The PL studies exhibit several bands characteristic of Cr3+ ions in octahedral symmetry.

Synthesis and spectral investigations of Mn(II) ions doped NaCaAlPO4F3phosphor

Mn(II) ions doped NaCaAlPO4F3 phosphor was synthesized by using solid state reaction method. The prepared sample was characterized by various spectroscopic techniques such as powder XRD, SEM with EDS, Optical absorption, electron paramagnetic resonance (EPR) and photoluminescence. From powder XRD, the average crystallite size was calculated about 46 nm. SEM images showed the irregular shaped entities present in the sample. Optical absorption spectrum gave the absorption bands in UV-VIS region which are the characteristic of Mn(II) ions in octahedral symmetry. The room temperature EPR spectrum exhibited a six weak hyperfine splitting lines centered at g = 2.0. Photoluminescence spectrum showed the emission peaks in visible region, from yellow to red with an excitation wavelength of 465 nm. From the emission spectral data, the CIE chromaticity coordinates were also calculated as (x = 0.661, y = 0.338).

Optical and EPR studies of Gd2Zr2O7 phosphors prepared via solution combustion method

Phosphor powder of Gd2Zr2O7 has been prepared by the urea combustion route. Phase evolution of the synthesized powder is determined by X-ray diffraction (XRD) technique. The structural environment between the Gd3+ and the zirconium oxide lattice has been investigated using electron paramagnetic resonance (EPR), diffuse reflectance and photoluminescence (PL) studies. The EPR spectrum of Gd2Zr2O7 phosphor exhibits a broad and intense signal at g≈2.0 and this has been attributed to Gd3+ ions in octahedral symmetry with strong dipolar interactions between Gd3+ ions. The intensity of the spectrum increases with temperature lowering from 296 to 110K following the usual Boltzmann law. The g value is invariant with temperature variation. The diffuse reflectance spectrum exhibits two sharp and weak bands characteristic of Gd3+ ions in octahedral symmetry. The photoluminescence spectrum exhibits several bands characteristic of Gd3+ ions in octahedral symmetry.

The structural, optical and magnetic parameter of manganese doped strontium zinc borate glasses

Glasses with composition 10SrO:(30−x)ZnO:60B2O3:xMnO, 0≤x≤0.9 (all compositions in wt%) have been prepared and investigated by X-ray diffraction, EPR, Optical absorption and FT-IR spectroscopic techniques. The XRD pattern of all the glasses confirmed the formation of an amorphous structure. The EPR spectra of all glass samples exhibit resonance signals at g≈2.0 with a sextet of hyperfine lines. The spin concentration (N) and temperature dependence of EPR signals were studied for Mn2+ ions in strontium zinc borate glass samples. The zero-field splitting parameter D has been evaluated from the intensities of the allowed hyperfine lines. The paramagnetic susceptibility (χ) was calculated from EPR data at different temperatures and the Curie temperature (θp) was calculated from the 1/χ verses T graph. The optical absorption spectra exhibit a single broad band near 470nm and this has been attributed to the spin-allowed 5Eg→5T2g transition of Mn3+ ions in octahedral symmetry. The theoretical optical basicity (Λth) of these glasses have also been evaluated. The FTIR studies show BO3 and BO4 structural units in strontium zinc borate glasses.

Use of Fe3+ ion probe to study the structural coordination in sodium–lead borophosphate glasses by utilizing electron paramagnetic resonance and optical spectroscopy

Electron paramagnetic resonance (EPR) and optical absorption spectral investigations have been carried out on Fe3+ ions doped in sodium–lead borophosphate glasses. The EPR spectra exhibit resonance signals with effective g values at g≈1.99, g≈4.30 and g≈8.40. The resonance signal at g≈8.40 has been attributed to Fe3+ ions in axial symmetry sites whereas the resonance at g≈4.30 is due to rhombic symmetry site. The g≈1.99 resonance is due to Fe3+ ions coupled by exchange interaction in a distorted octahedral environment. The EPR spectra at different temperatures (93–303K) have also been studied. The intensity of the resonance signals decreases with increase in temperature whereas linewidth is found to be independent of temperature. The paramagnetic susceptibility (χ) was calculated from the EPR data at various temperatures and the Curie constant (C) and paramagnetic Curie temperature (θp) have been evaluated from the 1/χ versus T graph. The optical absorption spectrum exhibits three bands characteristic of Fe3+ ions in octahedral symmetry. The crystal field parameter (Dq) and the Racah interelectronic repulsion parameters (B and C) have also been evaluated and discussed. The optical band gap energy (Eopt) and Urbach energy (ΔE) are calculated from their ultra-violet absorption edges. Photoluminescence spectra show prominent blue emission peaks under near band edge UV excitation. The FT-IR spectrum shows that the glass system contains BO3, BO4 and PO4 structural units.

Physical and spectral investigations of Mn2+ ions doped poly vinyl alcohol capped ZnSe nanoparticles

Abstract Mn2+ doped ZnSe nanoparticles are prepared by using poly vinyl alcohol (PVA) as capping agent. Various physical parameters are calculated for the prepared sample and spectroscopic techniques such as XRD, optical, electron paramagnetic resonance (EPR) and FT-IR studies have been carried out. The particle size is characterized by powder X-ray diffraction and it is about 21 nm as calculated by Scherrer’s formula. The EPR spectrum at room temperature exhibits sextet hyperfine structure centered at g ≈ 2·0, characteristic of Mn2+ ions in octahedral symmetry. EPR and optical absorption studies reveal that the site symmetry of Mn2+ is predominantly octahedral. Crystal field and inter-electronic parameters are evaluated. FT-IR spectrum exhibits bands, which are attributed to O H, C H, C C and C O groups of stretching and bending vibrations.