Local Crystal Environment Research Articles

Double perovskite CaSrMSbO6(M = La, Gd, Y): Bi3+ phosphors for multifunctional application

Bi3+-doping luminescent materials have recently evoked considerable interest in versatile applications. In this work, we have developed a series of Bi3+-activated CaSrMSbO6(M = La, Gd, Y) phosphors with double perovskite structures, exhibiting blue emission from 350 nm to 500 nm. The emission spectral position and intensity of Bi3+ ions can be tuned by changing excitation wavelength and doping concentrations. The relationship between the local crystal field environment and the luminescence properties is comprehensively analyzed. Importantly, optical temperature properties of CaSrLaSbO6: Bi3+ were investigated and were found to reach a maximum relative sensitivity of 4.57 % K−1 at 298 K. Furthermore, the anti-counterfeiting ink was prepared using CaSrLaSbO6: Bi3+ phosphors, and it showed tunable emission under different light stimulation. These results indicate that CaSrLaSbO6: Bi3+ phosphors have application potential in optical temperature sensing and anti-counterfeiting.

Quantifying Covalency and Environmental Effects in RASSCF-Simulated O K-Edge XANES of Uranyl.

A RASSCF approach to simulate the O K-edge XANES spectra of uranyl is employed, utilizing three models that progressively improve the representation of the local crystal environment. Simulations successfully reproduce the observed three-peak profile of the experimental spectrum and confirm peak assignments made by Denning. The [UO2Cl4]2- model offers the best agreement with experiment, with peak positions (to within 1 eV) and relative peak separations accurately reproduced. Establishing a direct link between a specific electronic transition and peak intensity is complicated, as a large number of possible transitions can contribute to the overall peak profile. Furthermore, a relationship between oxygen character in the antibonding orbital and the strength of the transition breaks down when using a variety of orbital composition approaches at larger excitation energy. Covalency analysis of the U-O bond in both the ground- and excited-state reveals a dependence on the crystal environment. Orbital composition analysis reveals an underestimation of the uranium contribution to ground-state bonding orbitals when probing O K-edge core-excited states, regardless of the uranyl model employed. However, improving the environmental model provides core-excited state electronic structures that are better representative of that of the ground-state, validating their use in the determination of covalency and bonding.

A Lu3Sc2Ga3O12: Eu3+ red-emitting phosphor with excellent optical properties and thermal stability was obtained by partially replacing Lu3+ with Gd3+ / Y3+

A novel red phosphor Lu3(1-x)Sc2Ga3O12: xEu3+(0 ≤ x ≤ 0.3) was successfully prepared by high temperature solid state method. The Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor shows strong high internal quantum efficiency and thermal stability with values of 64.79 % and 87.0 %, respectively. Based on Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor, the partial replacement of Lu3+ ions in the host by Gd3+ / Y3+ ions changes the local crystal field environment of Eu3+ ions, resulting in wonderful changes in the luminous center, and the luminous intensity at 593 nm is increased by 3.66 and 3.54 times, respectively. The decay time of Eu3+ ions is analyzed from the perspective of dynamics, and the reasons for the enhancement of luminescence after partial replacement of Lu3+ ions are discussed in detail from two aspects of phosphor structure and crystal field effect around Eu3+ ions. In addition, with the substitution of Gd3+ / Y3+ ions, the thermal stability of the sample is 90.3 %/89.4 % with excellent low thermal quenching. The thermal quenching mechanism is described by combining Debye temperature and activation energy. The sample also has a high internal quantum efficiency IQE=79.03 % / 78.24 %. Finally, under the excitation of 365 nm chip, the phosphors of Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ and Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Y3+ synthesized R-LED device has extremely high color rendering index, Ra is 78.23/77.15 and color temperature is 1640.38 K/1642.97 K. The experimental results show that the Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ / Y3+ phosphors prepared has a wide application prospect in w-LED devices.

Effects of Gd3+ and Ga3+ substitution on the local structure and luminescence properties of Y0.97Al3(BO3)4: 0.03Dy3+ single-phase phosphors

A series of Y1-x-yAl3–3z(BO3)4: xDy3+, yGd3+ and zGa3+ single-phase phosphors were prepared by solid-phase technique. Subsequently, the samples were analyzed by Rietveld refinement, SEM, FT-IR and XPS to determine their phases, morphologies, and compositions. The results show that Dy3+, Gd3+ and Ga3+ were successfully doped in YAl3(BO3)4 and the prepared phase was very pure without changing the structure of the initial phase. The emission peaks of Y1-xAl3(BO3)4: xDy3+ phosphor at λex= 351 nm are 483 nm and 574 nm, which correspond to 4F9/2 → 6H15/2 and 6H13/2 transitions, respectively. Afterwards, the local crystal field environment of Dy3+ in the luminescence center was improved by replacing Y3+ with Gd3+ and Al3+ with Ga3+, which enhanced the luminescence. At the peak at 574 nm, the doping of Gd3+ increased 1.49 times and that of Ga3+ increased 1.98 times. The internal quantum efficiencies of these two phosphors are as high as 67.23 % and 70.86 %, and the thermal stabilities are 86.7 % and 88.4 %, respectively. We discuss the mechanism of introducing Gd3+ and Ga3+ to produce luminescence enhancement from two aspects. On the one hand, the host activity was analyzed and explained by first-principles calculations combined with diffuse reflectance spectroscopy. On the other hand, dipole moments are introduced to control the local aberration parameters. Finally, 365 nm chip was used to package and test Y0.94Al3(BO3)4: 0.03Dy3+, 0.03Gd3+ and Y0.97Al2.7(BO3)4: 0.03Dy3+, 0.1Ga3+ phosphors. The color rendering indices of the samples was 67.4 and 68.1, respectively, and they emitted bright natural white light. The results indicate that the Y0.94Al3(BO3)4: 0.03Dy3+, 0.03Gd3+ and Y0.97Al2.7(BO3)4: 0.03Dy3+, 0.1Ga3+ single-phase phosphors have potential commercial value as W-led devices.

Magnetic hyperfine interactions of probe 57Fe atoms within the hexagonal manganite ScMnO3

Here we present the Mössbauer study of the combined magnetic and electrical hyperfine interactions of the probe 57Fe nuclei localized in the hexagonal manganite ScMnO3. The hyperfine interactions were measured in the temperature range where ScMnO3 demonstrates spin ordering: 15 K <T <TN (∼ 130 K). By analyzing the hyperfine parameters of 57Fe nuclei, we evaluated the oxidation state of the iron ions, their local crystal environment, and the orientation of the magnetic moments μFe in the structure of ScMn0.99657Fe0.004O3 at T <<TN. The temperature-dependent evolution of Zeeman structures in Mössbauer spectra was analyzed using the stochastic relaxation model, and indicates the presence of frustration of the superexchange interactions Fe3+−O−Mn3+. The temperature dependence of the hyperfine magnetic field Bhf(T) was described using critical indices, whose values reflect the reduced dimensionality of the magnetic system under study. It was shown that the observed sharp temperature-dependent change of the quadrupole shift of the Zeeman structure components may be attributed to the spin reorientation process, resulting in antiferromagnetism with a weak ferromagnetic component.

Ratiometric mechanoluminescence in LiSrPO4:Eu2+/Eu3+ for stress sensing: Dopant concentration dependent sensitivity

Ratiometric mechanoluminescence (ML) has been recently proposed for stress-sensing, which is regarded to be superior to the traditional ML-intensity based sensing route in terms of accuracy and cycle stability. The dual-activator strategy to realize the ratiometric ML takes advantage of instantaneous change of local crystal field environment induced by stress, where the structural characteristics of host are supposed to play major role. Herein, LiSrPO4:Eu2+/Eu3+ phosphors have been explored to realize the ratiometric ML, with the focus on the influence of Eu dopant concentration on the sensitivity of the stress-dependent ratiometric ML. The dependence between the dopant concentration and sensitivity can be interpreted in terms of host phase structure evolution with dopant concentration.

Effect of local crystal field environment on luminous properties of Er3+/Yb3+-doped titanate upconversion luminescent materials

The upconversion luminescence performance is closely related to the local crystal field environment. However, it is challenging to achieve an ideal luminescence performance by local crystal structure engineering. In this work, four titanate upconversion luminescent materials with fixed elemental compositions were synthesized, which enabled systematic exploration effects of the local crystal field environment (local structure symmetry and interatomic distance) on the upconversion performance. When the effects of local structure symmetry and interatomic distance on upconversion performance were taken into account individually, it was not easy to precisely characterize how the local crystal field environment influenced the upconversion performance. Thus, to illustrate this issue, we established a mathematical model that can satisfactorily describe the variation trend of the red/green integrated intensity ratio in terms of the product of local crystal field intensity and interatomic distance. This finding provides an excellent theoretical basis for the design of luminescent materials with ideal upconversion performance.

Co-substitution strategy to achieve a novel efficient deep-red-emitting SrKYTeO6:Mn4+ phosphor for plant cultivation lighting

Mn4+-doped oxide phosphors with bright red emission show promising application potential in plant cultivation lighting. However, finding suitable oxide hosts for Mn4+ ions incorporation is still a challenge. Herein, an efficient deep-red-emitting SrKYTeO6:Mn4+ phosphor was achieved through the co-substitution of [K+−Y3+] for [Sr2+−Ca2+] in non-luminous Sr2CaTeO6:Mn4+ for the first time. Crystal structure analysis reveals that the new SrKYTeO6 compound is isostructural to Sr2CaTeO6, which belongs to the monoclinic P21/n (14) space group. Upon 338 nm excitation, the SrKYTeO6:Mn4+ phosphor exhibits a deep-red emission band peaking at 680 nm, resulting from the 2Eg → 4A2 g transition of Mn4+ ion. The concentration of Mn4+ ion in SrKYTeO6 is optimized to be 0.4 mol%, and color purity and internal quantum efficiency (IQE) of this phosphor reach as high as 98.5% and 44.3%, respectively. The phosphor also possesses good thermal stability with the emission intensity at 423 K maintaining 56% of the initial value at 298 K. These superior luminescent properties could be attributed to the change of local crystal environment induced by distorting the internal [TeO6] octahedra. This work not only acquires an efficient SrKYTeO6:Mn4+ phosphor for application in plant cultivation lighting but also offers a replicable strategy for further exploring novel Mn4+-doped perovskite phosphors.

Charge ordering in Ir dimers in the ground state of Ba5AlIr2O11

It has been well established experimentally that the interplay of electronic correlations and spin-orbit interactions in ${\mathrm{Ir}}^{4+}$ and ${\mathrm{Ir}}^{5+}$ oxides results in insulating ${J}_{\mathrm{eff}}=1/2$ and ${J}_{\mathrm{eff}}=0$ ground states, respectively. However, in compounds where the structural dimerization of iridium ions is favorable, the direct Ir $d\text{\ensuremath{-}}d$ hybridization can be significant and takes a key role. Here, we investigate the effects of direct Ir $d\text{\ensuremath{-}}d$ hybridization in comparison with electronic correlations and spin-orbit coupling in ${\mathrm{Ba}}_{5}{\mathrm{AlIr}}_{2}{\mathrm{O}}_{11}$, a compound with Ir dimers. Using a combination of ab initio many-body wave-function quantum chemistry calculations and resonant inelastic x-ray scattering experiments, we elucidate the electronic structure of ${\mathrm{Ba}}_{5}{\mathrm{AlIr}}_{2}{\mathrm{O}}_{11}$. We find excellent agreement between the calculated and the measured spin-orbit excitations. Contrary to expectations, the analysis of the many-body wave function shows that the two Ir (${\mathrm{Ir}}^{4+}$ and ${\mathrm{Ir}}^{5+}$) ions in the ${\mathrm{Ir}}_{2}{\mathrm{O}}_{9}$ dimer unit in this compound preserve their local ${J}_{\mathrm{eff}}$ character close to 1/2 and 0, respectively. The local point group symmetry at each of the Ir ions plays an important role, significantly limiting the direct $d\text{\ensuremath{-}}d$ hybridization. Our results emphasize that minute details in the local crystal field environment can lead to dramatic differences in the electronic states in iridates and $5d$ oxides in general.

Design of Ratiometric Dual‐Emitting Mechanoluminescence: Lanthanide/Transition‐Metal Combination Strategy

AbstractMechanoluminescence (ML) materials with the ability to convert mechanical stimulate into visible light signals have enabled visualized mechanics sensing. To this point, stress sensing based on ML color is preferred over that based on ML intensity in terms of both sensing reliability and visual sensitivity. In this work, a ratiometric dual‐emitting ML strategy to realize the stress‐sensitive ML color variation, where the Lanthanide/transition‐metal combination is adopted to build the dual‐activator ML system is proposed. The difference in electronic configuration between Lanthanide and transition‐metal ions leads to the significant discrepancy in the response of corresponding luminescence kinetics to the instantaneous change of local crystal field environment induced by stress, which plays a key role in the strategy. This strategy establishes a new general path for the design of novel ratiometric ML materials.

Crystal structure, dielectric, and ferroelectric characteristics of zirconate tantalate ceramics with tungsten bronze structure

In the present work, dielectric and ferroelectric characteristics of Ba6−pRpZr2+pTa8−pO30 (p = 1, 2, R = La, Nd, Sm) tungsten bronze ceramics were investigated systematically, and the effects of Zr4+ and Ta4+ occupation upon the polar order were emphasized. X-ray diffraction patterns confirmed the tetragonal tungsten bronze structure with P4/mbm space group at ambient temperature. Relaxor ferroelectric behavior was determined for all compounds, even for those who had order A1- and A2-site occupations, and this was quite different from other tungsten bronze systems. Compared with the Ti- and Nb-based analogue, these Zr- and Ta-based compounds exhibited stronger relaxor nature and obvious polar order disruption. Raman spectra and X-ray photoelectron spectra demonstrated distinct local crystal environment for these compounds with different B-site substitutions. Smaller A-site cation displacement inside the pentagonal channels, frustrating BO6 deformation, and weaker B–O-bond covalency were the main reasons for the severe disruption of ferroelectric polar order in these filled tungsten bronzes.

Local atomic and crystal structure of rapidly quenched TiNiCu shape memory alloys with high copper content

This study aims to reveal features of the local crystal structure and environment in the quasi-binary TiNi–TiCu alloys containing 25–40 at.% Cu, by X-ray diffraction and EXAFS spectroscopy. The alloys were produced in an amorphous state by the melt-spinning technique and then crystallised by isothermal and electropulsing treatment. It was shown that Ni local structure is more disordered in comparison with Cu local environment, which is closer to the conventional crystallographic structure. An increase in the Cu content resulted in the magnification of the disordering in the nearest local environment, around both the Ni and Cu atoms, consisting of Ti atoms. No noticeable effect of the annealing rate on the local structure was found.

Manipulation of upconversion property and enhancement of sensitivity by tailoring the local structure

AbstractTailoring the local crystal environment around the activators is one of an important way to enhance the upconversion (UC) luminescence intensity. Herein, we substitute the Y3+ lattice with La3+ ion gradually in Y2Ti2O7:Yb3+, Er3+ phosphor and investigate the effect of La3+ concentration on the UC luminescent properties as well as the temperature sensing behaviors. During the phase transformation process from cubic Y2Ti2O7 to monoclinic La2Ti2O7, the La3+ ions also play an important role on the adjustment of size and morphology of particles. Furthermore, the cooperation of La3+ ion is in favor of the crystal growth toward the easy growth directions. The UC luminescence intensities can be enhanced efficiently with the increasing of La3+ concentration. The sensitivity for temperature sensing can be improved by the increasing of La3+ concentration in the Y2Ti2O7 and La2Ti2O7 two‐phase coexistence system and the maximum SA is 45.3 × 10−4 K−1 at 410K when the La3+ concentration is 80%. The maximum SA and corresponding temperature can be adjusted by controlling the La3+ concentration, which means that (Y0.94‐xLax)2Ti2O7: Er3+/Yb3+ phosphors may be applicable to different working environment.

Simulation of Carbo‐Nitride Precipitation in the Multi‐Phase Microstructure of Micro‐Alloyed Transformation‐Induced Plasticity Steel

During the thermo‐mechanical treatment of low‐carbon transformation‐induced plasticity (TRIP) steel, precipitation of micro‐alloying carbo‐nitrides occurs in a complex microstructure consisting of various phases and mixtures of these, such as austenite, ferrite, pearlite, bainite, and/or martensite. In addition, the precipitation process is commonly stimulated and accelerated by plastic deformation that is induced by hot and warm rolling. In the present contribution, a method is suggested, which allows for a thermokinetics‐based simulation of the amount as well as the type and distribution of secondary precipitates depending on the local chemical and crystal environment of the polymorph microstructure. As basis of this study serves the thermokinetic software package MatCalc, it is used to simulate the evolution of precipitates during the entire steel processing route. According to the present simulation results, the distribution of C among individual precipitation domains, i.e., phases, is the most important factor governing the precipitate evolution in the system. In addition, the simulations show that niobium carbide (NbC) and vanadium carbide (VC) precipitates differ in their nucleation and growth behavior during the thermo‐mechanical treatment. While NbC nucleates mainly during the hot rolling process in a purely austenitic matrix, VC predominantly forms at lower temperatures in ferrite.

Hyperfine field studies of the high-pressure phase of noncentrosymmetric superconductor RhGe (B20) doped with hafnium

We have used the time differential perturbed angular correlation (TDPAC) spectroscopy to measure the electric and magnetic hyperfine fields in RhGe crystallized in the B20 cubic lattice structure and weakly doped with Hf (0.5–2 atomic %) in the temperature range from 5 K to 295 K. Two most commonly used nuclei probes, 111In→111Cd and 181Hf→181Ta, have been used. The experimental results combined with theoretical density functional calculations indicate that the In/Cd impurities substitute into the Ge-site whereas the Ta/Hf probes substitute into the Rh-site. It has also been found that the Ta/Hf impurity strongly distorts the local crystal environment, whereas the effect from the In/Cd probe is weak. There are no reliable evidences of the magnetic order in the studied alloys at low temperatures.

Freud: A software suite for high throughput analysis of particle simulation data

The freud Python package is a library for analyzing simulation data. Written with modern simulation and data analysis workflows in mind, freud provides a Python interface to fast, parallelized C++ routines that run efficiently on laptops, workstations, and supercomputing clusters. The package provides the core tools for finding particle neighbors in periodic systems, and offers a uniform API to a wide variety of methods implemented using these tools. As such, freud users can access standard methods such as the radial distribution function as well as newer, more specialized methods such as the potential of mean force and torque and local crystal environment analysis with equal ease. Rather than providing its own trajectory data structure, freud operates either directly on NumPy arrays or on trajectory data structures provided by other Python packages. This design allows freud to transparently interface with many trajectory file formats by leveraging the file parsing abilities of other trajectory management tools. By remaining agnostic to its data source, freud is suitable for analyzing any particle simulation, regardless of the original data representation or simulation method. When used for on-the-fly analysis in conjunction with scriptable simulation software such as HOOMD-blue, freud enables smart simulations that adapt to the current state of the system, allowing users to study phenomena such as nucleation and growth. Program summaryProgram Title:freudProgram Files doi:http://dx.doi.org/10.17632/v7wmv9xcct.1Licensing provisions: BSD 3-ClauseProgramming language: Python, C++Nature of problem: Simulations of coarse-grained, nano-scale, and colloidal particle systems typically require analyses specialized to a particular system. Certain more standardized techniques – including correlation functions, order parameters, and clustering – are computationally intensive tasks that must be carefully implemented to scale to the larger systems common in modern simulations.Solution method:freud performs a wide variety of particle system analyses, offering a Python API that interfaces with many other tools in computational molecular sciences via NumPy array inputs and outputs. The algorithms in freud leverage parallelized C++ to scale to large systems and enable real-time analysis. The library’s broad set of features encode few assumptions compared to other analysis packages, enabling analysis of a broader class of data ranging from biomolecular simulations to colloidal experiments.Additional comments including restrictions and unusual features:1. freud provides very fast parallel implementations of standard analysis methods like RDFs and correlation functions.2. freud includes the reference implementation for the potential of mean force and torque (PMFT).3. freud provides various novel methods for characterizing particle environments, including the calculation of descriptors useful for machine learning. The source code is hosted on GitHub (https://github.com/glotzerlab/freud), and documentation is available online (https://freud.readthedocs.io/). The package may be installed via pip install freud-analysis or conda install -c conda-forge freud.

Effect of the Phase Composition and Local Crystal Structure on the Transport Properties of the ZrO2–Y2O3 and ZrO2–Gd2O3 Solid Solutions

The results of investigating the crystal structure, ionic conductivity, and local structure of the (ZrO2)1 –x(Gd2O3)x and (ZrO2)1 –x(Y2O3)x (x = 0.04, 0.08, 0.10, 0.12, and 0.14) solid solutions are reported. The crystals are grown by directional crystallization of the melt in a cold container. The phase composition of the crystals is investigated by X-ray diffractometry and transmission electron microscopy. The transport characteristics are studied by impedance spectroscopy in the temperature range of 400 to 900°C. The local crystal structure is examined by optical spectroscopy. Eu3+ ions were used as a spectroscopic probe. The study of the local structure of the ZrO2–Y2O3 and ZrO2–Gd2O3 solid solutions revealed the features in the formation of optical centers, which reflect the character of localization of oxygen vacancies in the crystal lattice depending on the stabilizing oxide concentration. It is established that the local crystal environment of Eu3+ ions in the (ZrO2)1 –x(Y2O3)x and (ZrO2)1 –x(Gd2O3)x solid solutions is determined by the stabilizing oxide concentration and is practically independent of the stabilizing oxide type (Y2O3 or Gd2O3). The maximum conductivity at a temperature of 900°C is observed in the crystals with 10 mol % of Gd2O3 and 8 mol % of Y2O3. These compositions correspond to the t'' phase and are close to the interface between the cubic and tetragonal phase regions. It is found that in the ZrO2–Y2O3 system the highly symmetric phase is stabilized at a lower stabilizing oxide concentration than in the ZrO2–Gd2O3 system. The analysis of the data obtained makes it possible to conclude that, in this composition range, the concentration dependence of the ionic conductivity is mainly affected by the phase composition rather than the character of the localization of oxygen vacancies in the crystal lattice.

Influence of phase composition and local crystal structure on the transport properties of ZrO2−Y2O3 and ZrO2−Gd2O3 solid solutions

Abstract. The results of investigation of crystal structure, ion conductivity and local structure of solid solutions (ZrO2)1−x(Gd2O3)x and (ZrO2)1−x(Y2O3)x (x = 0.04, 0.08, 0.10, 0.12, 0.14). The crystals were grown by directional crystallization of the melt in a cold container. The phase composition of the crystals was studied by X−ray diffractometry and transmission electron microscopy. Transport characteristics were studied by impedance spectroscopy in the temperature range 400—900 °C. The local crystal structure was studied by optical spectroscopy. Eu3+ ions were used as a spectroscopic probe. The results of the study of the local structure of solid solutions of ZrO2—Y2O3 and ZrO2—Gd2O3 systems revealed the peculiarities of the formation of optical centers, which reflect the nature of the localization of oxygen vacancies in the crystal lattice depending on the stabilizing oxide concentration. It is established that the local crystal environment of Eu3+ Ions in solid solutions (ZrO2)1−x(Y2O3)x and (ZrO2)1−x(Gd2O3)x is determined by the stabilizing oxide concentration and practically does not depend on the type of stabilizing oxide (Y2O3 or Gd2O3). The maximum conductivity at 900 °C was observed in crystals containing 10 mol.% Gd2O3 and 8 mol.% Y2O3. These compositions correspond to the t′′−phase and are close to the boundary between the regions of the cubic and tetragonal phases. It was found that in the system ZrO2—Y2O3 stabilization of the highly symmetric phase occurs at a lower stabilizing oxide concentration than in the system ZrO2—Gd2O3. Analysis of the data obtained allows us to conclude that in this range of compositions the main influence on the concentration dependence of the ion conductivity has a phase composition, rather than the nature of the localization of oxygen vacancies in the crystal lattice.

Ba3P4O13:Eu3+ phosphors with high thermal stability and high internal quantum efficiency for near-ultraviolet white light-emitting diodes

The studied samples, which were sintered by a sol–gel technique, can be efficiently pumped by the near-ultraviolet light and emitted bright red light arising from the 4f–4f transitions of Eu3+ ions. Besides, color coordinate and internal quantum efficiency of the synthesized phosphors were determined to be (0.621, 0.378) and 71.2%, respectively. The optimum doping concentration for the Eu3+ ions in the Ba3P4O13 host lattices was revealed to be 10 mol% and the concentration quenching mechanism was dominated by electric-dipole interaction. By a facile method utilizing the Judd–Ofelt theory, the intensity parameters were calculated to analyze the local crystal environment surrounding the Eu3+ ions in the Ba3P4O13 host lattices. Furthermore, the temperature-dependent PL emission spectra confirmed that the studied compounds still remained 80.7% of its initial PL emission intensity at room temperature, indicating its excellent thermal stability. Ultimately, a light-emitting diode device, which can emit bright white light with proper correlated color temperature (CCT = 6727 K) and color rendering index (CRI = 73.2) values, was packaged to explore the feasibility of the final products for indoor illumination applications.

Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties

Eu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO2-55GeO2 synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A diffusion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements confirmed the dispersion of BTG nanocrystals of size 20–100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs.