Jumpei Ueda

Japan Advanced Institute of Science and Technology

Persistent phosphors show contentious luminescence even after ceasing excitation light. This unique phenomenon is caused by several processes such as carrier generation, trapping and detrapping. Based on the mechanism, persistent luminescence can be designed by controlling the carrier transportation. By utilizing the vacuum referred binding energy...

Persistent luminescence is caused by a charge carrier detrapping process from the carrier traps filled by excitation light. Thus, the carrier storage capacity is an important factor in determining the persistent luminescence intensity. Here, the electron storage capacity was investigated in the YAGG:Ce³⁺-Yb³⁺ transparent ceramic persistent phosphor...

Lanthanide ions act as excellent luminescence centers and as good charge carrier traps. By selecting proper lanthanide ions, persistent phosphors with the desired luminescent color can be developed. In addition, an appropriate host material can give not only better persistent luminescence performance but also an additional function. We successfully...

We investigated thermally activated ionization and thermally activated crossover as the two possibilities of quenching of 5d luminescence in Pr3+-doped Y3Al5−xGaxO12. Varying the Ga content x gives the control over the relative energy level location of the 5d and 4f2:PJ3 states of Pr3+ and the host conduction band (CB). Temperature-dependent lumine...

Trivalent europium (Eu3+) ions show red luminescence with sharp spectral lines owing to the intraconfigurational 4f-4f transitions. Because of their characteristic luminescence properties, various Eu3+-doped inorganic compounds have been developed to meet the demands of optoelectronic devices. Regardless of shielding by the outer 5s and 5p orbitals...

Lanthanide ion doped garnet is one of the representative persistent luminescence (PersL) phosphors that have been widely investigated. However, the role of the trap centers, either intentionally added co‐dopants or intrinsic defects arising during the sintering process, and their effect on the performance of PersL has not been completely elucidated...

A Near-Infrared (NIR) ratiometric luminescence thermometer with the composition of Yb1Gd2Al1.98Cr0.02Ga3O12 was prepared and studied. When excited by 660 nm in the first biological transparent window (BTW), the sample shows a peak structure of around 1000 nm due to the 2F5/2 → 2F7/2 transitions of Yb3+ via the energy transfer process from Cr3+. Due...

Research of luminescent thermometer has predominantly centered around visible-light thermometers, susceptible to significant impact from Raleigh scattering (~λ−4). In this work, Cr4+ and Yb3+ co-doped Y3Al5O12 thermometer is reported. Both emission and excitation are in the infrared range, which makes this thermometer much less affected by Raleigh...

Based on the 4I13/2 → 4I15/2 emission (1450–1700 nm) of Er3+ in garnet, which is matching well with third bioimaging window (NIR-III), we propose a ratiometric near-infrared (NIR) thermometer (YAGG:Ce-Er) in NIR-III by utilizing thermal coupling between Stark levels of 4I13/2, where energy levels were split into seven sublevels (I–VII). The energy...

Nd³⁺-doped Y3Al2Ga3O12 garnet ceramic pellet was prepared by solid state reaction and used as prototype to investigate the potential of Nd³⁺-activated garnet phosphors as Boltzmann thermometers for cryogenic and high temperature ranges. Despite the conventional use of the near-infrared emitting Nd³⁺-activated phosphors for biological applications,...

Multifunctional phosphors with photochromism and persistent luminescent (PersL) properties have attracted increasing interest owing to the capability of absorbing the photon energy and trapping the generated carriers via defects. However, the opacity of materials compromises the enhancement of photochromism and PersL properties; besides, the need o...

Blue-light-excitable red-emitting phosphors with high thermal stability are essential for fabricating white light-emitting diodes (WLEDs). Herein, Ce3+-doped SrLaScO4 (SLO:Ce3+) phosphor is discovered to have an abnormal red emission band centered at 640 nm when excited at 440 nm. Spectroscopy and structural analyses confirm that Ce3+ ions occupy t...

Persistent luminescence (PersL) materials with diverse PersL colors hold great promise for glow-in-the-dark applications. However, extensive research has been devoted to merely altering the crystal field surrounding the activators and...

Red glass containing gold nano particles has attracted people because of its vivid red color. Although this glass is called “(gold) ruby glass”, it does not include any ruby crystals. In this study, glass ceramics containing α-Al2O3 crystals were successfully prepared by quenching a mixture of glass composed liquid phase with a solid phase of α-Al2...

Charge transfer (CT) luminescence of different types of polyhedra, [WO5]4- in Ca3WO5Cl2 and [WO6]6- in Ca3WO6, is characterized by spectroscopic experiments and ab initio calculations. According to the geometry optimization, W6+ ions form five-fold [WO5]4- square pyramids in Ca3WO5Cl2 because of a large interatomic distance between W6+ and Cl- of 3...

The design and development of effective luminescent thermal sensors have been driving technological progress in many different fields ranging from catalysis to biology and microelectronics, to name a few. The ratiometric concept of using the ratio between two luminescent emissions of lanthanide-doped phosphors allows overcoming some limitations res...

The increasing attention on the unique properties of oxyhydride materials motivates the exploration of their potential applications in optical fields, and the theoretical studies of their luminescence properties are still under progress. Here, we report the experimental and theoretical high-pressure photoluminescence (PL) studies on Eu-activated Sr...

Mixed-halide perovskites have attracted great attention in applications of lighting and photovoltaic devices due to their excellent properties. Understanding the phase segregation mechanism of mixed-halide perovskite has significance for suppressing the performance degradation of optoelectronic devices. Herein, we investigate the mixed-halide perov...

As an anniversary event of International Year of Glass (IYOG), especially to help advertisement of IYOG in Japan, we devoted ourselves for half a year of making a glass poster, called “Ikka-ni Ichimai [the annual S&T (Science and Technology) poster for everyone, in Japanese]”. The title of the poster is “GLASS - The most universal modern material”,...

Understanding temperature and pressure co‐induced structural evolution of nanocrystals (NCs) is important for the design and application of heterostructure devices. However, the phase transition and band structure change are difficult to be analyzed under temperature and negative pressure co‐induced conditions. Here, an adjustable self‐straining st...

The monoclinic YSiO2N activated with Ce³⁺ ions was synthesized, and its luminescence spectra were investigated to reveal the energy level structure of the Ce³⁺: 5d excited states. Depending on excitation wavelengths, two types of photoluminescence bands in violet and blue regions are observed, which differ in spectral shapes and thermal quenching b...

Glass matrix embedding is an efficient way to improve the chemical and thermal stability of the halide perovskite QDs. However, CsPbX3 QDs exhibit distinct optical properties in different glass matrixes, including photoluminescence (PL) peak position, PL peak width, and optical band gap. In this work, the temperature-dependent PL spectra, absorptio...

The valence state of Eu ions doped in inorganic compounds is easily influenced by the synthesizing conditions. In this study, X-ray absorption spectroscopy revealed that almost half of Eu ions incorporated in the YSiO2N host were reduced into the divalent state through the sintering process at 1600 °C under a N2 gas atmosphere without any annealing...

By estimating the trap depth from the relative position of the zigzag curve of divalent lanthanoid ions and conduction band bottom, the YSiO2N:Ce³⁺-based blue persistent phosphors are developed, and their persistent luminescence and thermoluminescence properties are characterized to identify the electron trap distributions. Taking the nephelauxetic...

Mn⁴⁺ ions show red to deep-red luminescence due to the ²E→⁴A2 spin-forbidden transitions in several host materials. Especially, Mn⁴⁺-doped LaAlO3 with perovskite structure shows the deep red luminescence with a quite long wavelength around 730 nm in the first biological window. In this study, we investigated the temperature dependence of the photol...

The high-pressure structures of alkaline earth metal hydride-fluorides (AHFs) (A = Ca, Sr, Ba) were investigated up to 8 GPa. While AHF adopts the fluorite-type structure (Fm3[combining macron]m) at ambient pressure without anion ordering, the PbCl2-type (cotunnite-type) structure (Pnma) is formed by pressurization, with a declining trend of critic...

The photoluminescence spectra and luminescence lifetimes of Eu³⁺-doped oxyhalides, YOX:Eu³⁺ (X = Cl or Br), and their temperature dependence on different halide species of mixed-anion coordinations were investigated and analyzed. In terms of the ionic and covalent nature of bonding, Eu³⁺ ions form different coordination polyhedra in the isostructur...

Understanding the role played by the material chemistry to increase the pressure sensitivity of new optical pressure probes is of great scientific interest. After almost 50 years from the first proposal as an optical pressure sensor, the R-line emission of ruby (α-Al2O3:Cr3+) is still the standard pressure probe used for the diamond anvil cell expe...

The performance of luminescent Cr³⁺‐doped thermometers is strongly influenced by the locally surrounding ligand field. A universal relationship between the thermometric performance and structural/chemical parameters is highly desirable to drive the development of effective Cr³⁺‐based thermal sensors avoiding trial‐and‐error procedures. In this view...

A single-crystalline defect-less phosphor is desired for efficient luminescence of the therein doped optical activators. In this paper, microsized MgAl2O4:Mn4+ single-crystal phosphors with bright red luminescence were grown in molten LiCl salt at 950 °C, for application in blue LED pumped white lighting. By comparing the phosphor formation from va...

Bismuth-based (nano)materials have been attracting increasing interest due to appealing properties such as high refractive indexes, intrinsic opacity, and structural distortions due to the stereochemistry of 6s2 lone pair electrons of Bi3+. However, the control over specific phases and strategies able to stabilize uniform bismuth-based (nano)materi...

After more than a century of studies on the optical properties of Bi3+ ions, the assignment of the nature of the emissions and the bands of the absorption spectra remain ambiguous. Here, we report an insight into the spectroscopy of Bi3+-activated CaMO3 perovskites (M = Zr, Sn, and Ti), discussing the factors driving the metal-to-metal charge trans...

Near-infrared (NIR) phosphors are fascinating materials that have numerous applications in diverse fields. In this study, a series of La3Ga5GeO14:Cr3+ phosphors, which was incorporated with Sn4+, Ba2+, and Sc3+, was successfully synthesized using solid-state reaction to explore every cationic site comprehensively. The crystal structures were well r...

Changing the electronic structure of materials by pressure and the accompanying changes in optical properties have attracted scientific interest. We have reported that the energy position of the conduction band (CB) bottom and the crystal field splitting of the Ce³⁺: 5d excited level in Y3Al5-xGaxO12: Ce³⁺ are changed by applying pressure, which re...

Luminescent Boltzmann thermometry is one of the most reliable techniques to locally probe the temperature in a contactless mode. However, to date, there is no report on cryogenic thermometers based on the highly sensitive and reliable Boltzmann-based ⁴T2→⁴A2/²E→⁴A2 emission ratio of Cr³⁺. Based on structural information of the local HfO6 octahedral...

In this work, the kinetic study of charge carriers trapping processes, photocurrent excitation measurements, and high-pressure spectroscopy investigation of optically stimulated luminescence (OSL) process in Lu2O3:Tb,Hf ceramics are presented. OSL process was experimentally and theoretically treated to explain the OSL mechanism and kinetics. Obtain...

Ratiometric optical thermometry is one of the most promising techniques for contactless temperature sensing. However, despite the efforts devoted in the last decades, the development of nanothermometers characterized by high reliability along with suitable sensitivity (Sr>1 %·K⁻¹) and thermal resolution (δT<0.5 K) in the physiological temperature r...

Blue light pumped red luminescence with broadband and high photon-energy emission is highly desired for phosphor-converted white light-emitting diodes (LEDs), to achieve high color rendering index and high luminous efficacy. The Mn4+-doped red-emitting phosphors generally exhibit sharp vibrionic emissions associated with the parity and spin-forbidd...

The design of effective optical systems featuring high thermal sensitivity able to discriminate ever smaller variations of temperature in noncontact mode is of critical importance to face the challenges brought by the modern‐day technological revolution. If from one hand, the ratiometric optical thermometers based on Boltzmann distribution are demo...

We report a new material, BaCN2:Eu²⁺ for a very sensitive optical pressure sensor, 50 times more sensitive than ruby. Photoluminescence spectra of the BaCN2:Eu²⁺ phosphor was measured under hydrostatic pressures from ambient pressure to 5.34 GPa at room temperature. The peak wavelength of the luminescence was drastically red-shifted at a rate of 19...

The engineering of covalency and crystal field is a key point for the control of the 5d energy level of Eu²⁺. The hydride ion exhibits strong covalency, which results in the large 5d energy shifting by the nephelauxetic effect compared to their fluoride analogues. In this study, the Eu²⁺-doped K2MgH4 Ruddlesden-Popper (n=1) perovskite was prepared...

The development of nanomaterials with high sensitivity to external stimuli such as temperature, is critical to investigate the driving force of biological processes but also catalytic mechanisms in extreme environments. However, the instability of nano-objects at high temperatures and different environments is a serious drawback limiting often thei...

Orange persistent luminescence and photo-darkening phenomenon were observed after UV excitation in calcium-gallium-germanate (CGG) glass with the composition of 3CaO-1Ga2O3-3GeO2 prepared by a melt-quenching method. The CGG glass was characterized by using XRD (x-ray diffraction), DSC (differential scanning calorimetry) and Raman scattering analyse...

Phosphors that emit in deep-red spectral region is critical for the plant cultivation lighting-emitting diodes. Herein, ultrabroadband deep-red luminescence of Mn4+ in La4Ti3O12 was studied which showed intense zero phonon line emission. The double-perovskite structural La4Ti3O12 simultaneously contains two Ti4+ sites forming slightly- and highly-d...

The development of non-contact thermometers with self-control to specific temperatures to be used as control markers with an additional degree of reliability is a challenge in the field of thermal sensors. Herein, a strategy exploiting the wide tunability of an intrinsic feature of oxide perovskites such as the phase transition temperature to desig...

Bismuth-based fluoride nanocrystalline particles are recently attracting much attention as host for luminescent ions such as lanthanides (Ln) being proposed for lighting devices and for biological applications. However, a comprehensive investigation on the chemical properties of this family of materials, the growth of the nanoparticles and informat...

We report the synthesis and luminescence properties as well as band structure of a series of layered mixed-anion compounds, including a new layered mixed anion compound, Sr3Sc2Ag2Se2O5. The crystal structure, band structure, and optical properties of this new compound and of related compounds Sr3Sc2Cu2Ch2O5 (Ch:chalcogen = S, Se) are presented. The...

Cr2Se3 crystallizes in a NiAs-type structure and is antiferromagnetic with a Néel temperature TN = 43 K (M. Yuzuri, 1973). Here five samples with the nominal composition Cr2+xSe3 (x = 0.04, 0.02, 0, 0.04, 0.08) were prepared by solid state reaction and spark plasma sintering (SPS). The phase composition was characterised by X-ray diffraction (XRD...

The absorption and luminescence properties (centroid shift and crystal field splitting of 5d orbitals) of Ce3+-doped garnets are summarized from the viewpoints of chemical composition (electron negativity and optical basicity) and the local crystal structure of the Ce3+ ion (bond length and distortion). Clear trends exist between (1) the centroid s...

After more than a century of studies on the optical properties of Bi³⁺ ion, the assignment of the nature of the emissions and the bands of the absorption spectra remain ambiguous. Here we report an insight into the spectroscopy of Bi³⁺-activated CaMO3 perovskites (M=Zr, Sn, Ti), discussing the factors driving the metal-to-metal charge transfer and...

New results presented by Wang et al. showing the temperature dependence of the Y3Ga5O12:Ce³⁺ energy bandgap have been taken into account in the calculations of the changes of the energy distance between the lowest 5d state of Ce³⁺ and the edge of the conduction band. Our calculations show that the diminishing of the band gap energy with temperature...

Long persistent phosphors of garnet structures were developed in the Ce3+ doped yttrium aluminum gallate system by Cr3+ or Yb3+ codoping. Both Cr3+ and Yb3+ ions play a role of trapping electrons produced by photo-ionization process from excited Ce3+ ions. By taking advantage of cubic system of garnet, these phosphors can be formed into transparent...

A Near Infrared (NIR) persistent luminescent Ba[Mg2Al2N4]:Eu²⁺-Tm³⁺ phosphor chargeable by red light was prepared via solid state reaction from all-nitride starting materials. Rietveld refinement shows that the obtained sample correlated well with the standard. The Eu²⁺:5d-4f broad persistent luminescence band in the range from 600-800 nm can be ef...

The structural and luminescence properties of Ce³⁺-doped Y3Al4.75Si0.25O11.75N0.25 (YASiONG:Ce) oxynitride garnet phosphor have been investigated by neutron powder diffraction (NPD) and spectroscopic measurements,respectively. The obtained NPD pattern confirmed the presence of N atom in YASiONG:Ce by Rietveld structural refinement for the first tim...

ZnGa2O4:Cr3+ is a well-known deep red (persistent) phosphor with R-lines due to the 2E→4A2 spin-forbidden transition of Cr3+ ions between 690 and 750 nm. Recently, this system has attracted a great deal of interest for in-vivo bio-imaging. In this study, we investigated the temperature dependence of photoluminescence (PL) spectrum of ZnGa2O4:Cr3+ a...

Eu²⁺-Dy³⁺ co-doped barium silicate glass was prepared by a melt quenching method and cerammed at various temperatures between 800 and 1250 °C to obtain the glass ceramic (GC) persistent phosphors. The crystal phase of Ba5Si8O21 was primarily precipitated in the GC samples. The GC sample cerammed at 1250 °C (GC1250) exhibited the longest persistent...

The increasing interest in the development of ratiometric optical thermal sensors has led to a wide variety of new systems with promising properties. Among them, singly-doped ratiometric thermometers were recently demonstrated to be particularly reliable. With the aim to discuss the development of an ideal optical thermal sensor, a combined experim...

Persistent luminescence (PersL) in the short-wave infrared (SWIR: ~900-1700 nm) region has attracted much attention for potential biomedical imaging and night-vision surveillance applications. Although trivalent lanthanide (Ln3+) ions are considered to be one of the most promising luminescent centers working for this region, the lack of suitable pe...

Nowadays highly efficient red phosphors with blue or near-UV excitation are strongly required to improve performance of existing white LEDs. With this aim in view, the Eu³⁺-doped YSiO2N ceramics with the pseudo-wollastonite structure was fabricated and thoroughly studied spectroscopically. The presence of two anions – O²⁻ and N³⁻ − around Eu³⁺ ions...

Deep-trap persistent luminescence materials, due to their exceptional ability of energy storage and controllable photon release under external stimulation, have attracted considerable attention in the field of optical information storage. Currently, the lack of suitable materials is still the bottleneck that restrains their practical applications....

The luminescence properties of Ce³⁺-doped GdxY3-xAl5-ySiyO12-yNy (x = 0, 1 and 2; y = 0.25) oxynitride garnet phosphors were investigated and compared with corresponding oxide garnet phosphors (y = 0). The measured photoluminescence spectra exhibit redshift of the emission peak wavelength by the partial nitridation of oxide garnet phosphors because...

Oxyhydride compounds of GdHO and GdHO:Tb³⁺ were successfully prepared by solid state reaction of GdH3, Gd2O3 and Gd2O3:Tb³⁺ under H2 atmosphere. From the XRD analysis, GdHO belongs to cubic fluorite structure (space group Fm3 @#x0305;m, lattice parameter a = 5.38450(4) Å for GdHO and 5.38523(6) Å for GdHO:Tb), which is different from the tetragonal...

In this work we present results of photocurrent excitation spectroscopy (PCE) of Gd3Al2Ga3O12:Ce3+ (GAGG:Ce3+) and Gd3Ga5O12:Ce3+ (GGG:Ce3+) performed at temperatures ranging from 100 to 500 K supplemented by spectroscopic measurements (steady state and time resolved photoluminescence spectroscopy) performed at temperatures ranging from 10 – 500 K...

Thin films of YbB4 and YbB6 have been deposited on sapphire substrates via hybrid physical chemical vapor deposition (HPCVD) using elemental ytterbium and decaborane, B10H14, as sources. The deposition condition dependence of the composition, purity, crystallinity and electrical properties has been investigated using x-ray diffraction (XRD), reflec...

The Y3Al2Ga3O12:Ce³⁺-Cr³⁺ compound is one of the brightest persistent phosphors, but its persistent luminescence (PersL) duration is not so long due to the relatively shallow Cr³⁺ electron trap. Comparing the vacuum referred binding energy of the electron trapping state by Cr³⁺ and those by lanthanide ions, we selected Yb³⁺ as a deeper electron tra...

The effect of Zn substitution on the persistent luminescence properties of MgGeO3:Mn²⁺-Ln³⁺ (Ln = Eu and Yb) red phosphors was investigated. The intensity of the persistent luminescence of the Eu³⁺ co-doped phosphors increased with increasing Zn content, whereas that of the Yb³⁺ co-doped samples decreased. For both series of lanthanide co-doped sam...

A new polymorph of BaCN2 was obtained via a simple nitridation reaction of BaCO3 under an NH3 flow at 900 °C. The product was analyzed by single crystal X-ray diffraction and infrared spectroscopy, and found to have a tetragonal I4/mcm crystal structure (space group no. 140) with a = 0.60249(4) nm and c = 0.71924(5) nm. In this structure, each Ba²⁺...

Persistent luminescence (PersL) imaging without real-time external excitation has been regarded as the next generation of autofluorescence-free optical imaging technology. However, to achieve improved imaging resolution and deep tissue penetration, developing new near-infrared (NIR) persistent phosphors with intense and long duration PersL over 100...

CaAlSiN3:Eu²⁺ is a widely applied phosphor in white LEDs (w-LEDs) because of strong blue absorption and efficient red luminescence with high thermal quenching temperature. The good stability against thermal quenching has been well established, but the mechanism for the luminescence quenching at high temperatures has not been elucidated yet. In this...

We have been working on the Lu 2 O 3 :Ln,M (Ln= Pr/Tb, M= Ca, Sr, Ba, Ti, Hf, Nb, Ta) storage and persistent phosphors for more than ten years now. More recently we have discovered that also LuPO 4 :Eu shows ability to store energy when exposed to ionizing radiation. All the compositions share some characteristics. For example, they need high-tempe...

Orange persistent phosphors of Ca3Si2O7 (CSO) doped with Eu(2+) were strategically developed by codoping Sm(3+) or Tm(3+). First, a vacuum referred binding energy, VRBE, diagram of Ca3Si2O7 (CSO) was constructed from the measured spectroscopic data. By the zigzag curve of the divalent lanthanide ions in the VRBE diagram, Sm(3+) and Tm(3+) ions were...

In this paper, Mn²⁺ and Ln³⁺ (Ln = Eu, Yb) co-doped MgGeO3 phosphors were prepared by a solid state reaction technique, and their optical properties were investigated. Mn²⁺-doped samples exhibit persistent luminescence in the red region, peaking at 677 nm, because of the ⁴T1→⁶A1 transition of the Mn²⁺ ions under ultraviolet (UV) excitation. Based o...

We have developed a novel persistent phosphor of LaAlO3 perovskite doped with Er³⁺, Cr³⁺, and Sm³⁺ (LAO:Er–Cr–Sm), which exhibits long persistent luminescence (PersL) at 1553 nm due to the Er³⁺:⁴I13/2 → ⁴I15/2 transition as well as at 734 nm due to the Cr³⁺:²E(²G) → ⁴A2(⁴F) transition. The intense near-infrared (NIR) PersL bands from Cr³⁺ and Er³⁺...

The Y3Al5-xGaxO12(YAGG):Ce³⁺-Cr³⁺ persistent phosphor is one of the materials in which Cr³⁺ ions act as electron traps. The possibility of electron traps by other transition metal ions (TM³⁺, TM= Sc, Ti, V, Cr, Fe) was investigated and those electron trap depth was compared with each other. In the thermoluminescence (TL) glow curves, the YAGG:Ce³⁺...

The alternative current driven light emitting diode (AC-LED) lighting system has attracted a great deal of attention because of the high luminous efficiency and the simple electric circuit. However, this system causes the unacceptable flicker due to rapid fluctuations in the voltage of the power supply. In order to compensate the flicker effect in...

To elucidate the persistent luminescence mechanism of the Ce³⁺-Cr³⁺-codoped Y3Al2Ga3O12 garnet (YAGG), the valence states of Ce and Cr ions before and during UV charging were investigated by X-ray absorption near edge structure (XANES) spectroscopy. In the XANES spectra for Ce LIII and Cr K edges of YAGG:Ce³⁺-Cr³⁺ under UV illumination, the valence...

Garnet structure (A3B2C3O12) with three different cation sites is a very flexible host material widely used for w-LEDs, solid-state lasers, scintillators and so on. In this work, we have successfully developed six different Cr3+ doped garnets: Y3Ga4.99Cr0.01O12 (YGG:Cr), Gd3Ga4.99Cr0.01O12 (GGG:Cr), Lu3Ga4.99Cr0.01O12 (LuGG:Cr), Y3Sc1.99Cr0.01Ga3O1...

Persistent luminescent properties in Ce³⁺-Cr³⁺ codoped Gd3Al5−xGaxO12 garnet (GAGG:Ce-Cr) solid solution have been investigated. The persistent luminescent color is shifted from orange to yellowish green with increasing Ga content because Ce³⁺: 5d level splitting becomes much weaker. The depth of electron trap introduced by Cr codoping was estimate...

Optical and photoacoustic properties of Ce³⁺-doped lanthanide (Lu, Y, Gd) aluminum garnet were investigated. In the photoacoustic (PA) spectra, the 5d1 (lowest 5d level) band of Ce³⁺ was observed at around 450 nm in the obtained Ce³⁺-doped garnet samples. This result shows that a part of the excited energy is converted to thermal energy, which is g...

We investigated the effect of trivalent lanthanide substitution on a novel oxynitride persistent phosphor SrSi2AlO2N3:Eu(2+),Ln(3+), which shows green persistent luminescence for more than 2 h. First, an energy level diagram by using the host-referred binding energy (HRBE) scheme was constructed. The location of the energy levels of all divalent an...

We report bright green persistent phosphors of Ce³⁺, Bi³⁺ codoped Y3Al5-xGaxO12 (YAGG:Ce³⁺-Bi³⁺, x from 0 to 4) due to 5d→4 f transition of Ce³⁺ after blue excitation, in which Bi³⁺ related defects work as efficient electron traps. The trap depths, which can be tunable by changing Ga³⁺ content, x from 0.31 to 1.07 eV, were estimated by initial rise...

Detailed spectroscopic analysis of the electronic configuration of Cr³⁺ in Bi2Ga4O9 is reported. The material exhibits unique luminescent properties arising from the crystal field experienced by Cr³⁺, with simultaneous strong sharp and broadband near-infrared emissions from the ²E and ⁴T2 excited states, in a wide range of temperature. The system d...

We investigated photoluminescence (PL) and scintillation properties of Ce3+-doped Y3Al2Ga3O12 (Ce:YAGG) transparent ceramics synthesized by vacuum sintering with different Ce3+ concentrations (mol.%) from 0.3% to 1% (0.3%Ce:YAGG, 0.5%Ce:YAGG, 0.8%Ce:YAGG and 1%Ce:YAGG). The samples were synthesized by the vacuum sintering technique. The obtained sa...

The inefficient luminescence performance of Ce3+ activated glasses is primarily responsible for their commercial failure compared to the Ce3+ activated crystalline materials that are widely used as phosphors and scintillators. We observed that this behavior is explicitly related to the intrinsic characteristics of the host material. Here, we presen...

The AC-driven LED lighting system has attracted a great deal of attention because of the high luminous efficiency and the simple electric circuit. However, this system causes unacceptable flicker due to rapid fluctuations in the voltage of the power supply. To restrain the effect by using persistent phosphors, we investigated persistent properties...