Silicate Phosphors Research Articles

Studies on Up-Conversion Photoluminescence Exhibited by Er3+-Doped Akermanite (Di-Calcium Magnesium Silicate) Phosphors

Studies on Up-Conversion Photoluminescence Exhibited by Er3+-Doped Akermanite (Di-Calcium Magnesium Silicate) Phosphors

Delineating Dy3+ and Sm3+ in thermally stable strontium silicate apatites for multifunctional applications

The structural, optical and temperature dependent luminescence properties of a series of Sr2Y8-xREx(SiO4)6O2 (RE=Dy and Sm) silicate phosphors are investigated for their multifunctional applications. The phosphors were synthesized using the solid-state reaction route with varying doping levels and characterized for phase purity. X-ray Diffraction analysis revealed the hexagonal crystal structure of (Sr2RE2)(RE6)(SiO4)6O2, indicating the incorporation of rare earth (RE) ions into two distinct crystallographic sites, thereby augmenting the luminescence properties. Dy3+ doped compounds exhibit intense yellow emission, promising white light generation when paired with InGaN blue LED chips. Sm3+ doped samples show orange-red emission around 601 nm, attributed to multipole-multipole interactions, with rapid decay curves suitable for high-speed response LEDs. Correlated Color Temperature (CCT) values were computed to assess the commercial viability of these phosphors in luminescence applications and the role of lighting in the growth of indoor plants and office spaces is discussed. The Sr2Y7.8Dy0.2(SiO4)6O2 phosphor with remarkable quantum yield of 63.56% demonstrated a thermal stability of 0.27 eV with enhanced sensitivity of about 0.39% K−1 and Sr2Y7.8Sm0.2(SiO4)6O2 with stability around 0.31eV with sensitivity of 1.11% K⁻¹ at 100K reveals them as potential candidates for optical temperature sensing. These results declare the competence of synthesized novel silicate apatites in solid-state lighting and optical thermometry.

Comprehensive Review on Downconversion/Downshifting Silicate-Based Phosphors for Solar Cell Applications.

Insufficient utilization of the solar spectrum in commonly employed solar cells, stemming from a spectral mismatch between the solar spectrum and the solar cell's band gap, poses a barrier to enhancing solar cell efficiency. To overcome this challenge, downconverting silicate phosphors are employed in solar cells to capture the infrared spectrum of sunlight, thereby augmenting solar cell efficiency. Downconversion/downshifting involves in converting high-energy photons into one or two near-infrared (NIR) photons. Remarkably, silicate-based downconverting phosphors enhance solar cell sensitization, light scattering, antireflectivity, and stability. This review delves into the various energy transfer mechanisms utilized in silicate phosphors. The key aspects covered in this review encompass the development of silicate phosphors that emit NIR light and their synthesis process. The working principle of the solar cell and its parameters are discussed. The impacts of silicate phosphor size, coverage, volume concentration, and arrangement on solar cell performance are also explored. Furthermore, the study addresses several intriguing approaches for developing innovative silicate phosphors to enhance solar cell performance.

Eu2+ doping and Mg2+-coupled Zn2+, Ca2+ and Sr2+ cations induce tunable orange-blue luminescence in cordierite

A series of Mg2Al4Si5O18:xEu2+ (x = 0.2, 0.6, 1.4, 2.8, 6.0mol‰) and Mg2Al4Si5O18:0.05B, 1.4Eu2+ (BZn2+, Ca2+ and Sr2+) phosphors were prepared by high-temperature melt ice-water quenching and heat treatment. In this study, using Eu2+ ions as a structural probe, we investigated the effects of heat treatment temperature, Eu2+ ion concentration, and cation position on the crystal phase and local structure, triggering changes in the luminescent properties of the phosphor and achieving coordinated blue and red luminescence. Through heat treatment analysis, we proposed the formation process of the two phases of cordierite. The doping of different concentrations of Eu ions in cordierite triggers the phase transition of the host lattice. The molar distribution ratio of Eu2+ ions was calculated by Gaussian peak-splitting fitting to identify the detailed occupancy distribution of the Eu2+ ions in μ-cordierite and α-cordierite. In the α-cordierite phase, with the doping of Zn2+, Ca2+, and Sr2+ cationic sites, the PL is modulated from orange to blue emission based on the selective occupancy of Eu2+ ions, which is caused by the difference in cationic radii and structural distortion. The comprehensive luminescence intensity of MASE1.4, MASZ0.05E1.4, MASC0.05E1.4, and MASS0.05E1.4 phosphors were 81.18%, 83.49%, 62.67%, and 76.41% at 150 °C compared to that at 30 °C, indicating the better thermal stability of the prepared phosphors. The luminescence tunable strategy by cation and Eu2+ doping simultaneously modifies the emission and achieves different thermal stability, providing a new design concept for the development of Eu2+-doped silicate phosphors.

Achieving high-efficiency green NaYSiO4:Tb phosphors by optimizing host structure through cation doping

Rare earth activated color converted phosphors have been widely used in solid-state lighting and display fields. Developing phosphors with high luminous efficiency is of great significance for light-emitting devices. Concentration quenching is the main factor limiting the improvement of phosphor luminescence efficiency during increasing the activator doping level. In this study, a novel structural optimization strategy is developed to overcome the impact of concentration quenching. In Tb3+ activated NaYSiO4 (NYSO), large-size Gd3+ ions are introduced to adjust the distance of rare earth ions and suppress the energy transfer between Tb3+ luminescent centers. It is shown that at a critical Tb3+ concentration, for which concentration quenching tends to occur in NaYSiO4:Tb3+, Gd3+ incorporation successfully raises the internal quantum efficiency from 64.8 % for Tb3+-singly-doped NYSO up to 80.6 % for Gd3+/Tb3+ co-doped one. The findings can offer a feasible pathway in promoting the luminescent properties of silicate phosphor hosts.

Long wavelength near-infrared II emitting Na<sub>3</sub>YSi<sub>3</sub>O<sub>9</sub>:<i>x</i> Cr<sup>3+ </sup>silicate and spectral broadening by multi-site occupancy

Phosphors-converted near-infrared LED (pc-NIR LED) possesses applications in various fields including food quality analysis, night vision, biomedical imaging, and biomedicine. The design and development of broadband near-infrared (NIR) phosphors with the required properties are of decisive significance for pc-NIR LED devices. The Cr<sup>3+</sup> doped phosphors are considered to be most promising near-infrared materials for commercialization. Broadband NIR luminescent materials doped with Cr<sup>3+</sup> have attracted more and more attention due to their potential applications in NIR light sources. However, the emission wavelength of Cr<sup>3+</sup> doped phosphor is generally located in the NIR I region of less than 850 nm, and realizing the NIR II region emission is still a challenge. In this work, a series of Cr<sup>3+</sup> doped Na<sub>3</sub>YSi<sub>3</sub>O<sub>9</sub> new silicate phosphors is prepared by solid-state method in N<sub>2</sub> atmosphere at 1150 ℃ for 8 h. We take advantages of the silicate nature and the multi octahedral sites suitable for Cr<sup>3+</sup> in the studied Na<sub>3</sub>YSi<sub>3</sub>O<sub>9</sub> materials to redshift and broaden the spectrum. The phase, crystal structure, microstructure, photoluminescence, main emission peak decay and thermal stability of the samples are systematically studied. The results show that the prepared samples are pure phases, with uneven morphology, slight agglomeration, and the sizes in the micrometer range. The Cr<sup>3+</sup> is located in the weak crystal field environment of Na<sub>3</sub>YSi<sub>3</sub>O<sub>9</sub> lattice, with a <i>Dq</i>/<i>B</i> value of 2.29. Under the excitation of blue light at a wavelength of 485 nm, the strongest emission peaks of Na<sub>3</sub>Y<sub>1–<i>x</i></sub> Si<sub>3</sub>O<sub>9</sub>:<i>x</i> Cr<sup>3+</sup> phosphors are located at 984 nm (NIR II region), which is longer than those of most Cr<sup>3+</sup> activated phosphors. Due to the multi-site occupation of Cr<sup>3+</sup> in the lattice, the full width at half maximum (FWHM) of the emission spectrum is as high as 183 nm. The optimal doping concentration of Na<sub>3</sub>Y<sub>1–<i>x</i></sub> Si<sub>3</sub>O<sub>9</sub>:<i>x</i> Cr<sup>3+</sup> is 3%, and the quenching mechanism is the dipole-dipole interaction between Cr<sup>3+</sup> ions. Fluorescence decay curves show that the luminescence lifetime of Na<sub>3</sub>Y<sub>0.97</sub>Si<sub>3</sub>O<sub>9</sub>:0.03Cr<sup>3+</sup> sample gradually decreases with the increase of doping concentration and temperature. The results of the temperature-dependent spectra show that the emission intensity decreases in a temperature range from 298 K to 423 K, and the activation energy Δ<i>E</i> of Cr<sup>3+</sup> is 0.157 eV.

Thermally stable Cr3+-activated silicate phosphors for plant-growth LEDs and three-mode optical thermometry.

The structural, optical and temperature-dependent luminescence properties of Y2Mg2Al2Si2O12:Cr3+ phosphors were investigated for their multifunctional applications. The as-prepared phosphors exhibited an intense far-red emission band around 600-850 nm with a peak at 687 nm, which matches well with the absorption band of plant phytochromes. Importantly, the optimized sample showed excellent thermal stability and its emission intensity at 423 K maintained about 77% of that at 298 K. The potential application of the phosphors in plant-growth LED devices was also demonstrated. Furthermore, owing to the unique thermal quenching behavior of Cr3+, a three-mode luminescent thermometry system was designed based on fluorescent intensity (FL), fluorescent intensity ratio (FIR), and full width at half maximum (FWHM). The maximum temperature relative sensitivity (Sr) of each mode could reach 2.74% K-1, 1.09% K-1, and 1.47% K-1, respectively. These results indicate that the Y2Mg2Al2Si2O12:Cr3+ phosphors have potential applications for plant growth and optical thermometry.

Luminescence Properties of Ce-Doped Di-Calcium Magnesium Disilicate Ca2MgSi2O7:4 mol%Ce

Dicalcium magnesium disilicate (Ca2MgSi2O7) doped with cerium rare earth ions has been examined for its optical and photonic characteristics and applicability for radiation dosimetry applications. Mono-calcium aluminate that has cerium added to it, has been shown to be an excellent dosimeter with a linear response up to roughly 4 kGy of radiation exposures. Maximum TL emission is achieved at 4 mol% cerium dopant concentration. The clearly visible two peaks that were detected at 381.13K and 566.87K can be used as a high-temperature dosimetry advance. In this study, we reported the preparation technique and luminescence properties such as TL, ML, and PL of Ce3+ doped dicalcium magnesium silicate phosphors. The phosphors were prepared by the solid-state reaction method. The TL glow curves were recorded for all different concentrations of Ce- doped phosphors.

Identification of defect centers responsible for thermoluminescence emission in sol-gel synthesized calcium silicate phosphor

The thermoluminescence (TL) of calcium silicate phosphor (CSO) prepared by the sol-gel method and sintered at 1200 °C were investigated. From Tm-Tstop curve, TL emission spectrum and computer deconvolution using electron traps with discrete and continuous distributions, the glow curves were found to be composed of four TL peaks (117, 190, 250 and 275 °C) with a single emission band centered at 370 nm. Electron paramagnetic resonance (EPR) investigation has been carried out to identify the defect centers formed in the CSO phosphor by γ-irradiation and find the centers related to the TL process in the phosphor. At room temperature, three defect centers were observed. The first center, characterized by the principal g-values of 2.014, 2.011, and 2.0080 was assigned to an O− ion. The second center with g-values 2.015, 2.013, and 2.010 is also attributed to an O− ion and is associated with the TL peak at 280 °C. The third center, with an isotropic g-value of 2.0011 was identified as the F+ center (singly ionized oxygen vacancy) and relates to the TL peak at 280 °C.

TL, OSL, EPR, and defect centers in Tb-doped strontium silicate phosphor synthesized by a solid-state reaction method

Strong thermoluminescence (TL) was observed in Tb-doped strontium silicate phosphor prepared by the solid-state reaction method. Two glow peaks are observed at 100 and 190 °C. TL emission spectra indicate three recombination centers. The number of peaks and the kinetic parameters associated with the TL glow peaks of Tb-doped Sr2SiO4 phosphor after gamma irradiation were analyzed by Tm-Tstop and deconvolution methods. A study of defect centers induced by γ-irradiation and identification of defect centers responsible for the observed TL glow peaks has been carried out using the electron paramagnetic resonance (EPR) technique. The observed spectrum at room temperature is a superposition of at least three defect centers. Center I is characterized by an axially symmetric g-tensor with principal values g|| = 2.019, and g⊥ = 2.0013 and is ascribed to a O2− ion. Center II has a rhombic g-tensor with principal values 2.0072, 2.0024, and 1.995 and is assigned to an F+ center (singly ionized oxygen vacancy) and correlates with the 190 °C TL peak. The third center (center III) has an isotropic g-value of 1.991 and is identified as an F+ center.

Low temperature synthesis and enhancement of blue emitting CaMgSi2O6:Eu2+ phosphor by co-doping

Near UV excitable blue emitting Eu2+ activated CaMgSi2O6 phosphor has been synthesized by urea assisted pyrolysis technique. The effects of flux (H3BO3, NH4F, NH4Br, NH4Cl, CaF2, BaF2), sintering temperature (700–1100 °C), activator concentrations and co-dopants (Zn2+, Y3+, Al3+ and Gd3+) on the photoluminescence properties of CaMgSi2O6:Eu2+ were studied systematically. Zn2+, Y3+, Al3+ and Gd3+ co-doped CaMgSi2O6:Eu2+ phosphors improved the PL intensity and also exhibited a wide excitation band in the region of 250–420 nm, and emission at 447 nm found suitable for nUV based white LED applications. The PL emission intensity of Y3+ co-doped CaMgSi2O6:Eu2+ is comparable to that of the commercial BaMgAl1O17:Eu2+ blue emitting phosphor. However, Y3+ co-doped CaMgSi2O6:Eu2+ showed a higher thermal quenching when compared with BaMgAl1O17:Eu2+. The crystalline phase formation and morphology of synthesized silicate phosphors were confirmed by powder XRD and SEM analysis.

PVA-assisted synthesis of Zn2SiO4: Mn2+ nanoparticles: Enhanced luminescence properties and applications

Green-emitting Mn[Formula: see text] -doped zinc silicate nanophosphor was synthesized by solvothermal method with the assistance of polyvinyl alcohol (PVA). The structure, morphology and optical properties of phosphors were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR) and Photoluminescence Spectroscopy (PL). Also, the application of Mn[Formula: see text] -doped zinc silicate phosphor in electronic devices was studied. Furthermore, Zn2SiO4: Mn[Formula: see text] phosphor was used to be a fluorescent sensor for the first time to detect inorganic ions and small molecules. The results indicated that pure [Formula: see text]-Zn2SiO4 phase nanoparticles with spherical morphology were obtained. The results also showed that the phosphor has excellent selectivity and sensitivity for detecting Cr[Formula: see text] ions, Cr2O7[Formula: see text] ions and 4-nitrophenol (4-NP) with low detection limits (Cr[Formula: see text] ions: 1.34 [Formula: see text]M, Cr2O7[Formula: see text] ions: 5.86 [Formula: see text]M, 4-NP: 2.38 [Formula: see text]M). Thus, Mn[Formula: see text] -doped zinc silicate manganese phosphor has potential applications in light-emitting diodes (LEDs) and fluorescent sensors.

Structural, optical, and luminescence properties of Dy3+ -activated potassium calcium silicate phosphor for white light-emitting diodes.

A dysprosium (Dy3+ )-activated potassium calcium silicate (K4 CaSi3 O9 ) phosphor was prepared using a solid-state synthesis route. The phosphor had a cubic structure with the space group Pa as confirmed using X-ray diffraction (XRD) measurements. Details of surface morphology and elemental composition of the as-synthesized undoped KCS phosphor was obtained using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The chemical structure as well as the vibrational modes present in the as-prepared KCS phosphor was analyzed using Fourier transform infrared (FT-IR)spectroscopy. Diffuse reflectance spectra (DRS) were used to determine the optical bandgap of the phosphors and were found to be in the optical range 3.52-3.71 eV. Photoluminescence (PL) spectra showed intense yellow emission corresponding to the 4 F9/2 →6 H13/2 transition under 350 nm excitation. Commission International de l'Eclairage colour chromaticity coordinates were evaluated using the PL spectral data lie within the white region. Dexter theory and the Inokuti-Hirayama (I-H) model were applied to study the nature of the energy transfer mechanism in the as-prepared phosphors. The relatively high activation energy of the phosphors was evaluated using temperature-dependent PL (TDPL) data and confirmed the high thermal stability of the titled phosphor. The abovementioned results indicated that the as-prepared KCS:Dy3+ phosphor was a promising candidate for n-UV-based white light-emitting diodes.

Unveiling the luminescence of α-Zn2SiO4 phosphor: Profound influence of sintering temperatures

The zinc silicate (α-Zn2SiO4) phosphor was synthesized via a conventional sol-gel method, employing different sintering temperatures within the range of 800 to 1300 °C. To investigate the physicochemical properties of the α-Zn2SiO4 materials, a comprehensive range of analytical and spectroscopic techniques were utilized. In thermoluminescence (TL) measurements, the α-Zn2SiO4 sample sintered at 1200 °C exhibited a significantly higher intensity of glow peaks at around 115 °C and 304 °C. These enhanced glow peaks can be attributed to the presence of deep traps within the synthesized materials, which are activated upon X-ray irradiation. Additionally, dose-response measurements demonstrated a linear relationship between the TL glow peak intensity and the increment of X-ray dose. Furthermore, the photoluminescence (PL) analysis revealed that the synthesized α-Zn2SiO4 material emitted light at two distinct wavelengths at 463 nm and 542 nm which attributed to the possible electron-hole recombination of luminescent centres within the material. Combining the TL and PL results, the synthesized α-Zn2SiO4 material shows promise as a suitable candidate for dosimetry and lighting applications.

Synthesis and Optical Properties of Ce3+ Doped Gadolinium Silicate Phosphors

The present paper reports the optical properties of rare-earth-doped Gadolinium Silicate Phosphors. The Cerium Oxide (Ce3+) was used as rare-earth-doped. The phosphor is prepared by using the Solid-state reaction method (conventional method) heated at 1200oC for 2 hrs. The received cakes are grounded for 30 minutes each. The phosphors are prepared and the received powder is subjected to PL, XRD, SEM, and EDAX analysis. The following section discusses and the experimental results are mentioned in these phosphors. The present Phosphor can act as a host for blue light emission in many display devices and technological applications.

A novel K3(Y0.88Yb0.10Er0.02)Si2O7 silicate phosphor for multi-mode thermometry of high sensitivity through up-conversion luminescence

Non-contract optical thermometry shows great advantages for temperature measurement in harsh environments, and it is highly desired to develop novel and high-performance systems. In this work, a novel K3(Y0.88Yb0.10Er0.02)Si2O7 phosphor was synthesized via solid-state reaction, and its up-conversion luminescence and optical thermometric performance were systematically investigated. Under 980 nm excitation, the K3(Y0.88Yb0.10Er0.02)Si2O7 phosphor showed a strong green UC emission through a three photon process. The phosphor was found well capable of sensing temperature via the multi-modes of fluorescence intensity ratio (FIR) of thermally/non-thermally coupled energy levels and fluorescence lifetime (FL). The maximum absolute (SA) and relative (SR) sensitivities are SA = 156 × 10−4 K−1 (I531/I555, 298 K) and SR = 1.80% K−1 (I519/I555, 298 K) via the FIR mode, and are SA = 661 × 10−4 K−1 (548 K) and SR = 9.77% K−1 (298 K) via the FL mode, which are higher than those of most previous studies.

A potential red-light-emitting Pr3+-doped novel silicate phosphors: Judd–Ofelt analysis and photoluminescence properties

A potential red-light-emitting Pr3+-doped novel silicate phosphors: Judd–Ofelt analysis and photoluminescence properties

Tb3+ ion luminescence monitors β-dicalcium silicate mineralization conversion

Tb3+ doped β-dicalcium silicate (β-Ca2SiO4: Tb3+) phosphors with different concentrations of Tb3+ were successfully manufactured by the high-temperature solid-state method. The crystal structures, morphological, chemical composition, and optical performances of these before and after mineralization phosphors were investigated via X-ray diffraction, scanning electron microscopy, energy dispersives X-ray spectroscopy, as well as photoluminescence. The crystal structure of β-Ca2SiO4 can be stabilized by adding Tb3+ ions. Under 375 nm excitation wavelength, Tb3+ occurs on 5D4→7F5 transition, β-Ca2SiO4: Tb3+ phosphors exhibit intense green emission which is located at 543 nm. During the mineralization experiment, β-Ca2SiO4: Tb3+ phosphors showed good biological activity and were rapidly transformed into hydroxyapatite (HA), and its luminescence intensity attenuated synchronously. All results suggest that the mineralization process of β-Ca2SiO4: Tb3+ can be monitored by observing the change in luminescence intensity of Tb3+ ions.

Synthesis of Eu3+-Doped NaGd9Si6O26 Sub-Microcrystals from a NaGdF4@SiO2 Structure.

Rare earth silicate phosphors of high quantum efficiency with a stable performance are promising materials in the fields of display and illumination. The grain sizes of products synthesized via the conventional solid-state reaction method are usually too large to satisfy the requirements of color cast and extraction efficiency in high-resolution light-emitting devices (LEDs). We designed a synthetic route and successfully fabricated rare earth silicate NaGd9Si6O26 (NGSO) sub-microcrystals with a size ranging from 550 to 1200 nm. The reaction mechanism and optical properties were systematically investigated. The quantum efficiency of Eu3+-activated NGSO sub-microcrystals was about 36.6%. The LED encapsulated with these sub-microcrystals showed lower color deviation and higher lumen efficiency and lumen flux compared to that with NGSO fabricated using the conventional solid state reaction method.

Europium-Doped Calcium Silicate Nanoparticles as High-Quantum-Yield Red-Emitting Phosphors.

Europium ion-activated calcium silicate phosphors (Ca2SiO4:Eu3+) with sharp red-light emission were fabricated via the hydrothermal method. The size of Ca2SiO4:Eu3+ phosphors was controlled between 20 and 200 nm by precursor silicate particle sizes. Systematic studies to determine morphology, crystal phase, and photoluminescence (PL) were carried out for all the phosphors, and their optical efficiencies were compared. We found that the luminescence intensity and emission wavelength of Ca2SiO4:Eu3+ phosphors depend on their particle sizes. Particularly, the Ca2SiO4:Eu3+ synthesized with 20 nm silica seed contains the most intense red emission, high color purity, and high PL quantum yield. For the 20 nm-sized Ca2SiO4:Eu3+ phosphor, PL quantum yields are measured to be above 87.95% and high color purity of 99.8%. The unusually high intensity of 5D0 → 7F4 emission (712 nm) is explained by structural distortion arising from silicate particle size reductions. We show that the obtained phosphor is a suitable candidate for solid-state lighting as a red component through CIE chromaticity coordinate and color purity measurements. Furthermore, the Ca2SiO4:Eu3+ particles are examined for their validity as promising bio-imaging probes through cell labeling and imaging experiments and biodegradability studies.