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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

In Situ Neutron Diffraction Studies of the Ion Exchange Synthesis Mechanism of Li 2 Mg 2 P 3 O 9 N: Evidence for a Hidden Phase Transition

Motivated by predictions made using a bond valence sum difference map (BVS-DM) analysis, the novel Li-ion conductor Li 2 Mg 2 P 3 O 9 N was synthesized in this paper by ion exchange from a Na 2 Mg 2 P 3 O 9 N precursor. Impedance spectroscopy measurements indicate that Li 2 Mg 2 P 3 O 9 N has a room temperature Li-ion conductivity of about 10 –6 S/cm (comparable to LiPON), which is 6 orders of magnitude higher than the extrapolated Na-ion conductivity of Na 2 Mg 2 P 3 O 9 N at this temperature. The structure of Li 2 Mg 2 P 3 O 9 N was determined from ex situ synchrotron and time-of-flight neutron diffraction data to retain the P2 1 3 space group, though with a cubic lattice parameter of a = 9.11176(8) Å that is significantly smaller than the a = 9.2439(1) Å of Na 2 Mg 2 P 3 O 9 N. The two Li-ion sites are found to be very substantially displaced (~0.5 Å) relative to the analogous Na sites in the precursor phase. The non-molten salt ion exchange method used to prepare Li 2 Mg 2 P 3 O 9 N produces a minimal background in powder diffraction experiments, and was therefore exploited for the first time to follow a Li + /Na + ion exchange reaction using in situ powder neutron diffraction. Lattice parameter changes during ion exchange suggest that the reaction proceeds through a Na 2–x Li x Mg 2 P 3 O 9 N solid solution (stage 1) followed by a two-phase reaction (stage 2) to form Li 2 Mg 2 P 3 O 9 N. However, full Rietveld refinements of the in situ neutron diffraction data indicate that the actual transformation mechanism is more complex and instead involves two thermodynamically distinct solid solutions in which the Li exclusively occupies the Li1 site at low Li contents (stage 1a) and then migrates to the Li3 site at higher Li contents (stage 1b), a crossover driven by the different signs of the local volume change at these sites. Finally, in addition to highlighting the importance of obtaining full structural data in situ throughout the ion exchange process, these results provide insights into the general question of what constitutes a thermodynamic phase.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Structural modeling of high-entropy oxides battery anodes using x-ray absorption spectroscopy

High-entropy oxides (HEOs) are single phase solid solutions where five or more metals share the same sublattice, giving rise to unexpected features in various fields of applications. Recently, HEOs have emerged as an alternative conversion electrode anode material for next-generation Li-ion batteries, where the combination of several different elements in a single solid solution can synergistically act to overcome some of its main drawbacks, improving performance. Due to their chemical complexity, x-ray absorption spectroscopy (XAS) emerges as an appropriate technique to study the electronic (x-ray absorption near edge structure, XANES) and local structure (extended x-ray absorption fine structure, EXAFS) of these compounds as a function of cycling. This work aims to highlight the capabilities of XAS as an element-specific probe to understand a material’s structure at the atomistic level through EXAFS modeling of (MgFeCoNiCuZn)O high-entropy system and how to extract valuable information about the bond distance, number of near neighbors, and local disorder, which are crucial to a full understanding of the electrochemical reaction mechanisms of such battery electrodes.

25 ENERGY STORAGE↗
DOE OSTI2024

Structure–Composition Relationships for Mg–Ni and Mg–Fe Olivine

Olivine is a dynamic and important mineral in the crust and mantle with relevance to processes important to climate change technology, such as geologic carbon storage and critical mineral recovery. In this work, we critically evaluated and compiled a new database of olivine diffraction data, lattice parameters, and composition to enable rapid Ni-Mg-Fe olivine composition determination. A compilation of olivine X-ray diffraction data and chemical compositions from both the literature and the International Centre for Diffraction Data (ICDD) powder database was assembled to plot both the forsterite-fayalite and forsterite-liebenbergite solid solution lines. Here we present an expanded dataset to delineate equations and relationships used for quantifying the correlations between olivine lattice parameters and chemical compositions in Mg 2 SiO 4 -Fe 2 SiO 4 (forsterite-fayalite) and Mg 2 SiO 4 -Ni 2 SiO 4 (forsterite-liebenbergite) olivine solid solution series.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Atomic structural mechanism for ferroelectric-antiferroelectric transformation in perovskite NaNbO 3

Sodium niobate (NaNbO 3 or NN) is described as “the most complex perovskite system,” which exhibits transitions between, as well as coexistence of, several ferroelectrics (FE) and antiferroelectric (AFE) phases at different temperatures. Recently, solid solutions of NN with stabilized AFE phases(s) have gained attention for energy-related applications, such as high-density energy storage and electrocaloric cooling. A better understanding of the atomic mechanisms responsible for AFE/FE phase transitions in NaNbO 3 can enable a more rational design of its solid-solution systems with tunable functional properties. In this work, we have investigated changes in the average and local atomic structure of NN using a combination of x-ray/neutron diffraction and neutron pair-distribution function (PDF) analyses. The Rietveld refinement of the x-ray/neutron-diffraction patterns indicates a coexistence of the FE Q (P2 1 ma) and AFE P (Pbma) phases in the temperature range of 300 K ≤ T ≤ 615K, while PDF analysis indicated that the local structure (r < 8Å) is better described by a P2 1 ma symmetry. Above 615 K, the average structure transitions to an AFE R phase (Pmmn or Pnma), while PDF analysis shows an increased disordering of the octahedral distortions and Na displacements at the local scale. These results indicate that the average P/Q/R phase transitions in NN can be described as a result of complex ordering of distorted octahedral tilts at the nanoscale and off-centered displacements of the Na atoms.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Effect of samarium and iron substitution on the structural and magnetic properties of BaZr{sub 0.05}Ti{sub 0.95}O{sub 3} ceramics

Samarium and Iron doped barium zirconate titanate (SF-BZT) ceramics with general formula (SmFeO{sub 3}){sub x} - (BaZr{sub 0.05}Ti{sub 0.95}O{sub 3}){sub 1−x} (x = 0, 0.21, 0.22, 0.23) were prepared by solid state reaction route. X-Ray Diffraction revealed the proper phase formation and the profile matching with constant scale factor confirmed phase change from tetragonal to pseudo cubic with increase in samarium and iron content. The SEM micrographs show proper grain growth in samples. The magnetic data confirmed the presence of ferromagnetic character in the SF-BZT solid solutions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Additively-manufactured Al-0.3Zr-0.2Ce-0.2Cu alloy with high creep resistance and electrical conductivity

Here, a new, solute-lean Al-0.3Zr-0.2Ce-0.2Cu (wt.%) alloy is developed for additive manufacturing that overcomes the classical tradeoff between conductivity and creep resistance. The rapid-cooling-enabled supersaturation of Zr, and its uniform distribution in α-Al matrix, along with formation of submicron (Ce,Cu)-rich intermetallic particles on solidification lead to unusually high creep resistance at 200 °C. Near-zero secondary creep rates are achieved up to the alloy yield stress (YS) of 65 MPa at 200 °C in as-fabricated state. The Zr-solute-induced dislocation-climb suppression mechanism underlying this improvement also restricts dynamic recovery above YS, as noted from appreciable primary creep and its transitioning to near-zero secondary creep rates. A combination of relatively coarse, epitaxially-grown α-Al grains, low Zr concentration in α-Al, and the impurity-scavenging effect of Ce to purify α-Al matrix produces high electrical conductivity of ∼48 %IACS. Aging precipitation of L1 2 -Al 3 Zr nanoprecipitates doubles the YS (to ∼150 MPa) at room temperature and increases alloy conductivity to ∼58 %IACS, but loss of solid-solution Zr out of α-Al matrix leads to activation of dislocation climb, degrading the creep properties as compared to the supersaturated Al-Zr solid solution in the as-fabricated state. Compared to L1 2 -Al 3 Zr nanoprecipitates, submicron (Ce,Cu)-rich particles formed on solidification are more effective at impeding dislocation climb, producing a threshold stress for dislocation creep of ∼ 50 MPa at 200 °C. The new alloy design concepts, especially solute-induced dislocation-climb suppression for creep resistance, explored here may pave way for the design of new metallic alloys for thermal/electrical conductors and other high-temperature applications.

Additive Manufacturing↗
DOE OSTI2014

Accessing (Ba 1-x Sr x )Al 2 Si 2 O 8 :Eu Phosphors for Solid State White Lighting via Microwave-assisted Preparation: Tuning Emission Color by Coordination Environment

The preparation of Eu 2+ -substituted barium aluminum silicates is achieved using a rapid microwave-assisted preparation. The phase evolution of two BaAl 2 Si 2 O 8 :Eu 2+ polymorphs, the higher temperature hexagonal phase (hexacelsian), and the lower temperature monoclinic phase (celsian), is explored by varying the ramp time and soak time. This preparation method significantly reduces the reaction time needed to form these phases compared to conventional solid state routes. The luminescent properties of the two phases are identified under UV excitation with the hexagonal phase emitting in the UV region (λ em = 372 nm) and the monoclinic phase emitting in the blue region (λ em = 438 nm). The differences in optical properties of the two polymorphs are correlated to the coordination number and arrangement of the alkali earth site. The optical properties of the monoclinic phase can be further tuned through the substitution of Sr 2+ , forming the solid solution (Ba 1–x Sr x )Al 2 Si 2 O 8 :Eu 2+ . Changes in the crystal structure due to Sr 2+ substitution produce a surprising blue-shift in the emission spectrum, which is explained by a greater dispersion of bond lengths in the (Ba/Sr)–O polyhedra. The entire monoclinic solid solution exhibits excellent quantum yields of nearly 90 %, owing to the structural rigidity provided by the highly connected tetrahedral network.

Brgoch, Jakoah↗
DOE OSTI2024

Evidence of ordering in Cu-Ni alloys from experimental electronic entropy measurements

Phase diagrams exhibiting extended solid-solution and lenslike melting are often reproduced using ideal solutions, where ideal mixing considers a fully random configurational entropy of mixing. In the field of irreversible thermodynamics, experimental measurements of the composition variation of high-temperature electronic transport and molten-state properties suggest, however, a strong role for short-range atomic ordering in these systems. Herein, measurements of the thermopower and resistivity are reported for Cu-Ni solid solutions as a function of temperature and composition. The electronic transport properties were interpreted with an irreversible thermodynamic framework, revealing a large electronic contribution to the entropy of mixing. By considering a cluster model for the configurational entropy that uses the electronic contribution to inform the existence of ordered associates, we rationalize such a contribution of the electronic entropy with the ideal entropy of mixing commonly used to model such systems. In conclusion, these results suggest that the short-range order of the atoms plays a significant role in both solid and liquid states, even when there are no dominant intermetallic compounds in these alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Seebeck and Figure of Merit Enhancement by Rare Earth Doping in Yb14-xRExZnSb11 (x = 0.5)

Yb14ZnSb11 has been of interest for its intermediate valency and possible Kondo designation. It is one of the few transition metal compounds of the Ca14AlSb11 structure type that show metallic behavior. While the solid solution of Yb14Mn1-xZnxSb11 shows an improvement in the high temperature figure of merit of about 10% over Yb14MnSb11, there has been no investigation of optimization of the Zn containing phase. In an effort to expand the possible high temperature p-type thermoelectric materials with this structure type, the rare earth (RE) containing solid solution Yb14-xRExZnSb11 (RE = Y, La) was investigated. The substitution of a small amount of 3+ rare earth (RE) for Yb2+ was employed as a means of optimizing Yb14MnSb11 for use as a thermoelectric material. Yb14ZnSb11 is considered an intermediate valence Kondo system where some percentage of the Yb is formally 3+ and undergoes a reduction to 2+ at ~85 K. The substitution of a 3+ RE element could either replace the Yb3+ or add to the total amount of 3+ RE and provides changes to the electronic states. RE = Y, La were chosen as they represent the two extremes in size as substitutions for Yb: a similar and much larger size RE, respectively, compared with Yb3+. The composition x = 0.5 was chosen as that is the typical amount of RE element that can be substituted into Yb14MnSb11. These two new RE containing compositions show a significant improvement in Seebeck while decreasing thermal conductivity. The addition of RE increases the melting point of Yb14ZnSb11 so that the transport data from 300 K to 1275 K can be collected. The figure of merit is increased five times over that of Yb14ZnSb11 and provides a zT ~0.7 at 1275 K.

Kunz Wille, Elizabeth L. (ORCID:0000000228062663)↗
DOE OSTI2018

Two modes of screw dislocation glide in fcc single-phase concentrated alloys

Concentrated solid solution alloys (CSSAs), including medium- and high-entropy alloys, are currently being considered as prospective materials in many applications. The behavior of CSSAs under different conditions, including mechanical loading, differs from that of conventional alloys and has been the subject of intensive study by different techniques. In many cases, their behavior is treated by modifying solid solution hardening models, which, in principle, does not reflect many important features of CSSAs where the distinction between solute and solvent atoms is not clear. In this work, we report the results of an atomic-scale study of ½<110>{111} screw dislocation motion in an fcc equiatomic Ni-Fe alloy. Molecular dynamics simulations demonstrate that the dislocation has two distinctive modes for glide. At lower stress, dislocations move in a very rough manner that cannot be described as continuous glide but rather as jerky motion through a set of obstacles. At high stress, they glide in a manner similar to lattice friction-controlled conditions in single component systems. The stress for the transition between modes depends on the dislocation segment length and temperature. As a result, at 300 K, the flow stress saturates at ~130 MPa for lengths above ~140 |b| (b is the Burgers vector).

36 MATERIALS SCIENCE↗
DOE OSTI2018

Rare-earth high entropy alloys with hexagonal close-packed structure

The formation of octonary DyErGdHoLuScTbY and senary DyGdHoLaTbY and ErGdHoLaTbY high-entropy alloys (HEAs) with the hexagonal close-packed (HCP) structure was reported in this study. Experiments using scanning electron microscopy and x-ray diffraction confirmed the single HCP solid solution in the as-cast state for these three HEAs if the presence of minor rare-earth oxides due to contamination from processing is ignored. The measured compressive yield stress values for these HEAs at room temperature are 245, 205, and 360 MPa for the ErGdHoLaTbY, DyGdHoLaTbY, and DyErGdHoLuScTbY HEAs, respectively. As a result, the corresponding solid solution strengthening contributions for these HEAs were estimated using a simple elastic model, and the resulting contributions were 28 MPa, 27 MPa, and 42 MPa for the three aforementioned HEAs.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Revisiting the SGTE lattice stability of bcc aluminum

The CALPHAD framework rests on the ability to assign well-defined free energies to all phases, including mechanically unstable ones. Given the experimental difficulties associated with the latter, researchers have turned to computational methods to obtain a theoretically justified definition of the free energy of mechanically unstable phases. Recently, a method called “inflection detection” has been shown to yield free energies that are broadly consistent with the current SGTE (Scientific Group Thermodata Europe) standard for pure elements, which were obtained through an extrapolation of stable solid solutions free energies towards unstable end members. Despite this general agreement, apparent failures for a few elements stand out, notably for the bcc–fcc enthalpy difference for the common element Al. Furthermore we revisit the definition of the bcc Al enthalpy and show that a careful CALPHAD-based analysis of enthalpy trends in five different mechanically stable binary solid solutions in fact does agree very well with the inflection-detection approach.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

In this study, the formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O 3 . It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomic displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Wetting Behavior of Calcium Ferrite Slags on Cristobalite Substrates

Calcium ferrite (CF) is a significant intermediate adhesive phase in high-basicity sinters. The wettability between calcium ferrite (CF) and gangue plays an important role in the assimilation process. The wettability of CF-based slags, in which a constant amount (2 mass pct.) of Al{sub 2}O{sub 3}, MgO, SiO{sub 2}, and TiO{sub 2} was added, on solid SiO{sub 2} (cristobalite) substrates at 1523 K (1250 °C) was investigated. The interfacial microstructure and spreading mechanisms were discussed for each sample. All the tested slag samples exhibited good wettability on the SiO{sub 2} substrate. The initial apparent contact angles were in the range of 20 to 50 deg, while the final apparent contact angles were ~ 5 deg. The wetting process could be divided into three stages on the basis of the change in diameter, namely the “linear spreading” stage, “spreading rate reduction” stage, and “wetting equilibrium” stage. It was found that the CF-SiO{sub 2} wetting system exhibits dissolutive wetting and the dissolution of SiO{sub 2} into slag influences its spreading process. The spreading rate increases with a decrease in the ratio of viscosity to interfacial tension, which is a result of the addition of Al{sub 2}O{sub 3}, MgO, SiO{sub 2}, and TiO{sub 2}. After cooling, a deep corrosion pit was formed in the substrate and a diffusion layer was generated in front of the residual slag zone; further, some SiO{sub 2} and Fe{sub 2}O{sub 3} solid solutions precipitated in the slag.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A combined calorimetric and computational study of the energetics of rare earth substituted UO 2 systems

The energetics of rare earth substituted UO 2 solid solutions (U 1-x Ln x O 2-0.5x+y , where Ln = La, Y, and Nd) are explored employing a combination of calorimetric measurements and density functional theory based computations. Calculated and measured formation enthalpies agree within 10 kJ/mol for stoichiometric oxygen/metal compositions. To better understand the factors governing the stability and defect binding in rare earth substituted urania solid solutions, systematic trends in the energetics are investigated based on the present results and previous computational and experimental thermochemical studies of rare earth substituted fluorite oxides (A 1-x Ln x O 2-0.5x , where A = Hf, Zr, Ce, and Th). A consistent trend towards increased energetic stability with larger size mismatch between the smaller host tetravalent cation and the larger rare earth trivalent cation is found for both actinide and non-actinide fluorite oxide systems where aliovalent substitution of Ln cations is compensated by oxygen vacancies. Yet, the large exothermic oxidation enthalpy in the UO 2 based systems favors oxygen rich compositions where charge compensation occurs through the formation of uranium cations with higher oxidation states.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Structural and spectroscopic properties of high temperature prepared ZrO₂–TiO₂ mixed oxides

ZrO₂-TiO₂ mixed oxides of various composition, with the molar fraction of TiO₂ ranging from 0.1% to 15%, have been prepared via sol-gel synthesis and then calcined at 1273 K to check both their thermal stability and physicochemical properties. These solids are usually employed in photocatalytic processes and as active phase supports in heterogeneous catalysis. As indicated by X-ray diffraction and Raman spectroscopy, solid solutions based on Ti ions diluted in the ZrO₂ matrix are formed in the whole range of Ti molar fraction examined. Materials with low Ti loading (0.1%–1%) are basically constituted by the monoclinic phase of ZrO₂ while the tetragonal phase becomes prevalent at 15% of TiO₂ molar fraction. The presence of Ti ions modify the electronic structure of the solid as revealed by investigation of the optical properties. The typical band gap transition of ZrO₂ undergoes, in fact, a red shift roughly proportional to the Ti loading which reach the remarkable value of 1.6 eV for the sample with 10% of molar Ti concentration. Comparing chemical analysis of the solids with XPS data it has been put into evidence that the titanium ions distribution into the solid is not uniform and the concentration of Ti⁴⁺ tend to be higher in subsurface layers than in the crystal bulk. The introduction of titanium ions in the structure increases the reducibility of the solid. Annealing under vacuum at various temperatures causes oxygen depletion with consequent reduction of the solid which shows up mainly in terms of formation of Ti³⁺ reduced centres which are characterized by a typical EPR signal. Ti³⁺ defects forms, as also forecast by theoretical modelling of the solid, as their energy is lower than that of other possible reduced defective centers. The reduced solids are able to transfer electrons to adsorbed oxygen molecules in mild condition resulting in the formation of surface superoxide anions (O₂⁻) which are stabilized on surface Zr⁴⁺ or, alternatively, on Ti⁴⁺ ions according to the sample composition. - Graphical abstract: The presence of Ti in ZrO₂ modifies UV–vis and electronic properties of mixed oxides. Highlights: • ZrO₂–TiO₂ mixed oxides have been prepared via sol–gel synthesis. • Solids with low Ti loading are constituted by the monoclinic phase of ZrO₂. • The presence of Ti ions modify the electronic structure of the solid. • The introduction of titanium ions increases the reducibility of the solid.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Phonon scattering mechanisms dictating the thermal conductivity of lead zirconate titanate (PbZr 1- x Ti x O 3 ) thin films across the compositional phase diagram

This paper represents a thorough investigation of the thermal conductivity (κ) in both thin film and bulk PbZr 1–x Ti x O 3 (PZT) across the compositional phase diagram. Given the technological importance of PZT as a superb piezoelectric and ferroelectric material in devices and systems impacting a wide array of industries, this research serves to fill the gap in knowledge regarding the thermal properties. The thermal conductivities of both thin film and bulk PZT are found to vary by a considerable margin as a function of composition x. Additionally, we observe a discontinuity in κ in the vicinity of the morphotropic phase boundary (MPB, x = 0.48) where there is a 20%–25% decrease in κ in our thin film data, similar to that found in literature data for bulk PZT. The comparison between bulk and thin film materials highlights the sensitivity of κ to size effects such as film thickness and grain size even in disordered alloy/solid-solution materials. A model for the thermal conductivity of PZT as a function of composition (κ(x)) is presented, which enables the application of the virtual crystal approximation for alloy-type material systems with very different crystals structures, resulting in differing temperature trends for κ. We show that in the case of crystalline solid-solutions where the thermal conductivity of one of the parent materials exhibits glass-like temperature trends the compositional dependence of thermal conductivity is relatively constant for most values of x. Finally, this is in stark contrast with the typical trends of thermal conductivity with x in alloys, where the thermal conductivity increases dramatically as the composition of the alloy or solid-solution approaches that of a pure parent materials (i.e., as x = 0 or 1).

36 MATERIALS SCIENCE↗
DOE OSTI2017

Tunable Optical Properties and Increased Thermal Quenching in the Blue-Emitting Phosphor Series: Ba 2 (Y 1– x Lu x ) 5 B 5 O 17 :Ce 3+ ( x = 0–1)

The preparation of cerium-substituted barium lutetium borate, Ba2Lu5B5O17:Ce3+, is achieved using high temperature solid state synthesis. This compound crystallizes in the Ba2Y5B5O17-type structure and shows an efficient blue emission (λmax = 447 nm) when excited by UV-light (λex = 340 nm) with a photoluminescent quantum yield near 90%, a fast luminescence decay time (<40 ns), and a thermal quenching temperature of 452 K. Further, preparing a solid solution following Ba2(Y1–xLux)5B5O17:Ce3+ (x = 0, 0.25, 0.50, 0.75, 1) confirms that all compounds are isostructural and follow Vegard’s law. Substituting Y3+ for Lu3+ yields a nearly constant emission spectrum that blue-shifts by only 9 nm and has a consistent luminescence lifetime across the range prepared. The photoluminescent quantum yield (PLQY) and thermal quenching (T50) of the solid solution, however, are dramatically impacted by the composition, with the PLQY decreasing to ≈70% and the T50 dropping 49 K going from x = 1 to x = 0. These significant changes in the optical properties likely stem from enhanced structural rigidity as the larger, more polarizable Y3+ is substituted for the smaller, harder Lu3+ cation. These results highlight the importance of optimizing chemical bonding to improve a phosphor’s optical properties.

36 MATERIALS SCIENCE↗