Thermal Quenching Mechanism of Mn in NaSiF, NaKSiF, and KSiF Phosphors: Insights from the First-Principles Analysis.

This study aims to identify the key factors governing the thermal quenching of Mn ion luminescence in fluoride-based phosphor materials used as red emitters in modern-day phosphor-converted LED devices. Here, we employ first-principles calculations for Mn-doped NaSiF, NaKSiF, and KSiF hosts to explore how host properties and local coordination environments influence thermal quenching behavior. The ΔSCF method was used to model the geometric structures of the MnA (ground) and E, T (excited) states and the energies of the optical transitions between these states.

First-Principles Linear Combination of Atomic Orbitals Calculations of KSiF Crystal: Structural, Electronic, Elastic, Vibrational and Dielectric Properties.

The results of first-principles calculations of the structural, electronic, elastic, vibrational, dielectric and optical properties, as well as the Raman and infrared (IR) spectra, of potassium hexafluorosilicate (KSiF; KSF) crystal are discussed. KSF doped with manganese atoms (KSF:Mn) is known for its ability to function as a phosphor in white LED applications due to the efficient red emission from Mn⁴⁺ activator ions. The simulations were performed using the CRYSTAL23 computer code within the linear combination of atomic orbitals (LCAO) approximation of the density functional theory (DFT).

Unraveling Broadband Near-Infrared Luminescence in Cr-Doped CaYGeO Garnets: Insights from First-Principles Analysis.

In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr-doped CaYGeO garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of Cr activator ions, which revealed a pronounced preference for the Y sites over the Ca and Ge sites, as evidenced by the formation energy calculations. Subsequently, the geometric structures of the excited states E and T, along with their optical transition energies relative to the ground state A in CaYGeO:Cr, were successfully modeled using the ΔSCF method.

Effect of Covalence and Degree of Cation Order on the Luminous Efficacy of Mn Luminescence in the Double Perovskites, BaTaO ( = Y, Lu, Sc).

The spectroscopic properties of the Mn ion are investigated in the series of isostructural double perovskite compounds, BaTaO ( = Y, Lu, Sc). A comparison of these properties highlights the influence of covalent bonding within the perovskite framework and the degree of order between the B-Ta cations on the energy and intensity of the MnE → A emission transition (R-line). These two parameters of the emission spectrum are of importance for practical application since they determine the phosphor luminous efficacy.

Sensitive and Reliable Fluorescent Thermometer Based on a Red-Emitting LiMgHfO:Mn Phosphor.

Contactless fluorescent thermometers are rapidly gaining popularity due to their sensitivity and flexibility. However, the development of sensitive and reliable non-rare-earth-containing fluorescent thermometers remains a significant challenge. Here, a new rare-earth-free, red-emitting phosphor, LiMgHfO:Mn, was developed for temperature sensing.

Influence of Isostatic Pressure on the Elastic and Electronic Properties of KSiF:Mn.

Isostatic pressure effects on the elastic and electronic properties of non-doped and Mn-doped KSiF (KSF) have been investigated by first-principles calculations within density functional theory (DFT). Bulk modulus was obtained by the Murnaghan's equation of states (EOS) using the relationship between volume and pressures at pressures between 0 and 40 GPa, and elastic constants were calculated by the stress-strain relationship giving small distortions at each pressure point. The other elastic parameters such as shear modulus, sound velocity and Debye temperature, which can be obtained from the elastic constants, were also estimated.

Mn-Doped Heterodialkaline Fluorogermanate Red Phosphor with High Quantum Yield and Spectral Luminous Efficacy for Warm-White-Light-Emitting Device Application.

Narrow band red-emitting Mn-doped fluoride phosphor is an essential red component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF:Mn.

Luminescence and Cationic-Size-Driven Site Selection of Eu and Ce Ions in CaMg(SiO)Cl.

In this work, the morphology, composition, crystal, and electronic structure of CaMg(SiO)Cl (CMSOC) prepared by a high-temperature solid-state reaction technique are characterized first. To investigate the site occupancies of Eu and Ce in CMSOC, the emission spectra under well-chosen wavelength excitations and the corresponding excitation spectra by monitoring of the specific wavelength emissions are measured in detail for singly doped samples with different concentrations. Two kinds of Eu or Ce luminescence spectra are found.

Disorder-Induced Breaking of the Local Inversion Symmetry in Rhombohedral Pyrochlores MLaSbO (M = Mg or Ca): A Structural and Spectroscopic Investigation.

A detailed investigation of the overall crystal structure, and in particular of the local structure around the cations in MLaSbO (M = Mg, Ca) was accomplished using X-ray diffraction, steady state luminescence spectroscopy and decay kinetics, and state of the art density functional calculations. The computational tool was also used to investigate the structure of MnLaSbO. The Eu dopant ion was employed as an optical probe of the local symmetry at the cationic sites.

Control of Luminescence by Tuning of Crystal Symmetry and Local Structure in Mn -Activated Narrow Band Fluoride Phosphors.

Mn -doped fluoride phosphors have been widely used in wide-gamut backlighting devices because of their extremely narrow emission band. Solid solutions of Na (Si Ge )F :Mn and Na (Ge Ti )F :Mn were successfully synthesized to elucidate the behavior of the zero-phonon line (ZPL) in different structures. The ratio between ZPL and the highest emission intensity υ phonon sideband exhibits a strong relationship with luminescent decay rate.