High-temperature Solid-phase Method Research Articles

Luminescence and mineralization properties of Gd3+ stabilized β-dicalcium silicate

In this work, Gd3+-doped β-dicalcium silicate (β-Ca2SiO4) was resoundingly prepared by high-temperature solid-phase method. The crystal structure of Gd3+-doped β-Ca2SiO4 before and after mineralization was investigated by using X-ray diffraction method (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The scanning electron microscopy (SEM) was used to investigate the samples’ morphology. The chemical composition of Gd3+-doped β-Ca2SiO4 before and after mineralization was determined by X-ray energy-dispersive spectra (EDS). The luminescence properties of Gd3+-doped β-Ca2SiO4 before and after mineralization was investigated by photoluminescence (PL) spectroscopy. The experimental results show that Gd3+ ions have the effect of stabilizing β-Ca2SiO4, and Gd3+-doped β-Ca2SiO4 has good biological activity and can be rapidly converted to hydroxyapatite (HA). Meanwhile, with the prolongation of mineralization time, the luminescence intensity of Gd3+ ion decreases gradually. This suggests that the mineralization process of β-Ca2SiO4 can be monitored according to the luminescence intensity of Gd3+ ion.

Preparation and Luminescence Properties of K2MgSiO4:Mn4+ Phosphor

The K2MgSiO4:xMn4+ phosphor was synthesized by high temperature solid-p hase method and its luminescence characteristics were explored. The X-diffraction patt ern measured by the X-ray diffractometer matched well with the international standard card. The synthesized sample is a pure phase crystal, indicating that the doping of Mn 4+ has not changed The crystal structure of K2MgSiO4. Through the excitation and emi ssion spectra measured by the fluorescence spectrometer, it can be seen that the sample has 4 excitation peaks at 368nm, 422nm, 451nm and 534nm, and the maximum emissi on peak of the sample is at 654nm. By changing the doping concentration of Mn4+ ion s, it is found that as the Mn4+ concentration increases, the luminescence intensity of the sample increases, and finally the concentration quenching occurs after the concentrati on exceeds 1%. The chromaticity coordinates of the emission of the sample were meas ured to prove its role in the market. The chromaticity coordinates of the sample are loc ated in the red light zone and are close to the standard red light. The fluorescence lifeti me of Mn4+ transition on the D layer in the sample is about 0.2ms.

Preparation and Optical Properties of CaAlBO4:Eu3+Phosphor

A series of single-phase CaAlBO4: Eu3+ powder samples were synthesized by high-temperature solid-phase method, the main factors are temperature, time, concentration of rare-earth ion, etc. The results show that the maximum emission peak of the sample is located in the wide band spectrum of 467 nm, and belongs to the 4f65d to 4f7 transition of Eu3+. The maximum absorption peak is located at a narrow band of 678 nm. by a study of the relationship between the doping amount of Eu3+ and the luminescence property of the sample, The optimum doping content of Eu x 3+(x = 0.0025)

Study on Preparation and Luminescence Properties of Li2CaSiO4: Pr3+ Phosphor

In this paper, a high-temperature solid-phase method was used to synthesize Pr3+ ion-doped Li2CaSiO4 matrix phosphor. An X-ray diffractometer and a fluorescence transient spectrometer were used to characterize the crystal structure and luminescence properties of the prepared phosphors. The results show that the prepared sample is a single phase of Pr3+-doped Li2CaSiO4; it exhibits a good orange light emission under the excitation of blue light, and is expected to be used as white light LED lighting

Realization of high-quality white light emission in single-phased α-Sr2P2O7: Dy3+, Tm3+ phosphor

A single-phased white phosphor of α-Sr2P2O7: Dy3+, Tm3+ with low correlated color temperature (CCT) was synthesized by high temperature solid phase method. Our experimental results show that by co-doping Tm3+ and Dy3+ ions in the α-Sr2P2O7 matrix, the blue characteristic emission peak of Tm3+ ions can be used to effectively enhance the blue emission of the phosphor, and finally achieve high-quality white light emission. Moreover, since the emission spectrum of Tm3+ overlaps with the excitation spectrum of Dy3+ in the wavelength band from 445 to 465 nm, Tm3+ can transfer energy to Dy3+ ions, so the emission spectrum of Dy3+ can be further regulated and the emission intensity can be improved. Consequently, by optimizing the co-doping ratio of Tm3+ and Dy3+ ions, we achieved the optimal white light emission in α-Sr2P2O7: 0.01Tm3+, 0.01Dy3+ samples. Under the excitation of 351 nm ultraviolet light, the color coordinates of α-Sr2P2O7: 0.01Tm3+, 0.01Dy3+ emitting white light are (0.3292, 0.3521), and the CCT value is 5500 K, which are almost consistent with the color coordinates of standard white light and the color temperature of daylight. Therefore, α-Sr2P2O7: Dy3+, Tm3+ is a single-phased white phosphor material with great application potential for UV excitation.

Study on Luminescent Properties of Sr2MgTeO6:Tm3+ Blue-Emitting Phosphors

A series of solid solution blue-emitting tellurate Sr2MgTeO6:Tm3+ phosphors were prepared at 1100 °C by the high-temperature solid-phase method. The single phase of Sr2MgTeO6:xTm3+ (x = 0.0025-0.10 mol) were checked by powder X-ray powder diffraction. Under 359 nm excitation, the Sr2MgTeO6:Tm3+ phosphors emit blue emission at 456 nm. The optimum doping concentration was 0.05 mol. The fluorescent decay lifetime of Sr2MgTeO6:0.05Tm3+phosphor is 0.318 ms. These results validated the Sr2MgTeO6:Tm3+ tellurate phosphor showed the great potential in the field of solid lighting as blue-emitting substitutes.

Enhanced local symmetry achieved zero-thermal-quenching luminescence characteristic in the Ca2InSbO6:Sm3+ phosphors for w-LEDs

A material’s structure vitally affects its luminescence property, which in turn determines its application. Therefore, understanding the correspondence between structural local symmetry and luminescence characteristics is vital for the design and synthesis of optical materials. A series of solid solution reddish-orange-emitting phosphors Ca2InSbO6:Sm3+ (CISO:Sm3+) was synthesized by the high-temperature solid-phase method and applied for white-light-emitting diodes (w-LEDs). Under 407 nm excitation, CISO:Sm3+ phosphors showed intense reddish-orange emission at 600 nm that is attributed to the 4G5/2 → 6H7/2 transition of Sm3+ ions. Given that Sm3+ ions are a structural probe, the relationship between their local symmetry and luminescence properties was discussed in detail. The photoluminescence intensity of CISO:Sm3+ phosphors continuously increases with rising temperature from 298 to 480 K based on the enhanced local symmetry. This phenomenon was further analyzed using the trap theory and charge compensation mechanism. High color purity (~99.9%) and proper Commission International del′Eclairage (CIE) chromaticity coordinates were achieved for the CISO:Sm3+ phosphors. Finally, the fabricated w-LED displayed superior color rendering index (Ra = 93) and CIE chromaticity coordinates (0.330, 0.357) and thus has great potential as reddish-orange-emitting substitutes in horticultural and solid lighting. This work initiates a new insight to construct thermally stable phosphors for optical applications.

Luminescence Performance of BaGd2ZnO5 Microcrystalline Powder Doped with Different Rare Earth Ions

A group of BaGd2ZnO5 microcrystalline powders doped with Sm[Formula: see text], Dy[Formula: see text], Nd[Formula: see text] and Er[Formula: see text]/Yb[Formula: see text] were prepared by high temperature solid phase method, respectively. X-ray diffraction (XRD) analysis confirmed that all the products were pure BaGd2ZnO5 crystals, belonging to orthorhombic system and Pbnm space group. The emission spectra of Sm[Formula: see text], Dy[Formula: see text], Nd[Formula: see text] single-doped and Er[Formula: see text]/Yb[Formula: see text] double-doped samples under specific wavelength excitation were measured. The change of luminescence intensity at strong emission peak with doping concentration of doped ions was studied, and concentration quenching effect was found. The CIE color coordinates of the prepared samples were calculated. The results show that all coordinates doped with Sm[Formula: see text] are located in the orange red region. All coordinates of Dy[Formula: see text] doping samples are located in the yellow light region, but close to the white light region. All coordinates of Nd[Formula: see text] doping sample are located in the blue-green region. The upconversion luminescence of Er[Formula: see text]/Yb[Formula: see text] co-doped sample belongs to yellow light region.

Color-tunable Eu3+- or Sm3+-doped perovskite phosphors as optical temperature-sensing materials

Abstract Eu3+- or Sm3+-doped Sr2GaNbO6 perovskite phosphors are synthesized by a high-temperature solid-phase method, and their luminescence performance, energy transfer, and thermal sensitivity are studied. The results showed that Sr2GaNbO6 phosphor is an effective self-activated host, and successful doping with rare-earth ions is proven by their characteristic emission. At 332-nm excitation, both the broadband emissions from s-orbital mixing of the transition metal ions Nb5+ and Sr2+ and GaO6 groups and the sharp emissions from Eu3+ or Sm3+ ions are observed for Sr2GaNbO6:R3+ (R = Eu, Sm) phosphors, respectively. The emission color can be modulated from blue to white by regulating the doping concentration of Eu3+ or Sm3+, which is attributed to the effective energy transfer from s-orbital mixing of the transition metal ions Nb5+ and Sr2+ and GaO6 groups to Eu3+ or Sm3+. Based on the emission fluorescence intensity ratio of the s-orbital mixing of the transition metal ions Nb5+ and Sr2+ and GaO6 groups to the Eu3+ or Sm3+ ions in the range of 298–623 K, optical temperature sensing properties of Sr2GaNbO6:R3+ showed the maximum absolute and relative sensitivities are 0.0193 K−1 and 1.86% K−1 at 298 K of Sr2GaNbO6:0.018Eu3+ phosphor, respectively, as well as 0.00862 K–1 and 1.70% K−1 at 298 K and at 623 K, respectively, of Sr2GaNbO6:0.08Sm3+ phosphor. These results demonstrate a viable strategy to tune the emitting color and achieve optical temperature sensing in single-doped phosphors by controlling the energy transfer between the self-activated host and the activator. This strategy provides application potential for the white light-emitting diodes and non-contact thermometric multifunctional materials.

Synthesis and luminescent properties of LiLaSiO4:Dy3+, Eu3+ phosphors for white LEDs

A range of LiLaSiO4:xDy3+, yEu3+ phosphors were synthesized by high-temperature solid-phase method. Its phase composition, microstructure, luminescence properties, energy transfer mechanism, decay life and CIE color coordinates of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrometer. In LiLaSiO4:xDy3+ phosphors, as the doping concentration of Dy3+ increases, the luminescence intensity of Dy3+ increases first and then decreases, the concentration quenching point of Dy3+ was x ​= ​0.04. In LiLaSiO4: 0.04Dy3+, yEu3+ phosphors, as the doping concentration of Eu3+ increase, the luminescence intensity of Dy3+ decreases gradually. However, the luminescence intensity of Eu3+ increases first and then decreases, the concentration quenching point of Eu3+ was y ​= ​0.05. In LiLaSiO4:0.04Dy3+, yEu3+ phosphors, there is energy transfer between Dy3+ - Eu3+. When the concentration of Eu3+ was y ​= ​0.20, the energy transfer efficiency is 62.50%, The energy transfer mechanism of electric dipole-electric dipole LiLaSiO4:xDy3+, yEu3+ phosphor. By tuning the doping concentration percentage of Eu3+ and Dy3+, the LiLaSiO4:xDy3+, yEu3+ phosphors can realize the lighting by single-matrix warm white light-emitting diodes (WLEDs).

A high-sensitivity dual-mode optical thermometry based on one-step synthesis of Mn2+:BaAl12O19–Mn4+:SrAl12O19 solid solution phosphors

Compared with rare earth ions, transition metals have high temperature sensitivity, but the research on thermometry according to only using transition metals were not mentioned in phosphors. In this regard, a series of Mn2+:BaAl12O19–Mn4+:SrAl12O19 solid solutions were synthesized by high temperature solid phase method and researched. Although the sample is mixed phase, it can be synthesized in one step to avoid the defects in mixed phase preparation. The co-doping of Mn2+/Mn4+ is achieved by the self-reducing ability of BaAl12O19. It provides the possibility of thermometry doped Mn2+/Mn4+ based on the fluorescence intensity ratio. This material has excellent optical temperature sensing properties from 293 K to 406 K with good recyclability. Therefore, it is suitable for thermometry based on fluorescence intensity ratio with high maximum absolute (0.11 K−1 at 406 K) and relative sensitivity (4.37% K−1 at 293 K), obviously superior to the previously reported which are rare earth ions doped thermometry materials. Based on fluorescence lifetime of Mn4+, the maximum relative sensitivity is 4.48% K−1 at 353 K. The Mn2+/Mn4+ co-doped material is reported for the first time. The Mn2+:BaAl12O19–Mn4+:SrAl12O19 solid solutions have broad application prospect in the field of fluorescence thermometry, and the dual-mode thermometry makes it has excellent applicability in all aspects.

Experimental and theoretical studies on luminescent mechanisms and different visual color of the mixed system composed of MgGeO3:Mn, Eu and Zn2GeO4:Mn

In this work, the mixed system composed of Zn2GeO4: Mn and MgGeO3: Mn, Eu was synthesized by the high temperature solid phase method. Under the external excitation, visual color of samples was yellow. However, after the excitation was completed, visual color turned to be red. From luminescence spectrum, it was found that Zn2GeO4: Mn emitted green fluorescence of 534 nm under the excitation of 375 nm light. At the same time, MgGeO3: Mn, Eu emitted both fluorescence and persistent luminescence (PersL) of 668 nm. Moreover, the properties of PersL present samples were superior to other red PersL materials. Fine band structures from density functional theory (DFT) indicated that there were different luminescent mechanisms of Zn2GeO4: Mn and MgGeO3: Mn, Eu. When Zn2GeO4: Mn was excited, electron transitioned from VB to CB directly. Through CB, the electron was captured by the4T2(D) of Mn ion, then the electron jumped from4T2(D) to VB and recombined at once with the previous hole and emitted a 534 nm photon. When MgGeO3: Mn, Eu was excited, electron transitioned from6A1(S) of Mn ion to CB and left a hole. Through CB, electron was captured by7F6levels of Eu[Formula: see text] and remained metastable for a long time, which slowed down the recombined rate between electron and hole. Under thermal stimulation, the captured electron returned to CB from7F6levels and was recaptured by the4T2(D) of Mn. The electron transitioned down toward6A1(S) and recombined with the hole immediately, then emitted a photon with 668 nm.

Spectral study on energy transfer of the LiMgPO4 phosphor doped with Tm3+ and Tb3+

LiMgPO4(LMP):Tm, LMP:Tb and LMP:Tm, Tb phosphors were synthesized via a high-temperature solid-phase method, and the crystal structures of the samples were studied by X-ray diffraction (XRD). Thermoluminescence (TL) and optically stimulated luminescence (OSL) curves and TL three-dimensional (3D) spectra of the LMP phosphors doped with Tm3+ and Tb3+ were measured. The photoluminescence (PL) of the samples was also measured to study the effects of Tb3+ and Tm3+ ions on the luminescence of the material, its concentration on the luminescence properties, and the energy transfer between the two kinds of ions. The experimental results showed that in the co-doped system of LMP:Tm,Tb, the rare earth ions, Tm3+ and Tb3+, become the discrete luminescent centre, Tm3+ ions act as activators, and Tb3+ ions act as sensitizers. Upon analysing the PL lifetime of Tm3+ and Tb3+, energy transfer from Tb3+ to Tm3+ was found. According to the TL 3D spectra of LMP:Tm,Tb, the TL luminescence of Tb3+ below 200 °C was suppressed, and the TL luminescence of Tm3+ at approximately 300 °C was enhanced. This showed that the energy of the low-temperature glow peaks transferred to the 300 °C peak, meaning that the formation of shallow traps was inhibited, which is beneficial for the stability of the sample signal and improves the sensitivity of the sample to the high-temperature peak. Moreover, the TL and OSL intensities of the LMP:Tm, Tb phosphor were comparable to that of Al2O3:C; thus, it can be applied for a low-dose measurement.

Color tunable Eu-doped CaSrNb2O7 phosphors for white light-emitting diodes and optical thermometers

Herein, Eu-doped CaSrNb2O7 perovskites are synthesized by using the high-temperature solid-phase method, resulting in layered perovskite structure, with the space group of Cmc21 and a strong luminescence response under excitation wavelength of 314 nm. Moreover, these as-prepared CaSrNb2O7:xEu3+ (x = 0–0.15) phosphors are color-tunable. Specifically, the color changes from white to blue with raising temperature. After thermal stability testing, the fluorescence intensity ratio, maximum absolute and relative sensor sensitivity of CaSrNb2O7:xEu3+ are calculated to evaluate the thermal properties of materials. It turned out that the maximum absolute and relative sensor sensitivity are 0.043 K-1 and 0.0105 K-1, and the temperature resolution is as low as 0.0286K, respectively. It suggests that the high sensitivity and excellent resolution of CaSrNb2O7:xEu3+ make it a promising candidate for optical thermometers.

A novel blue-purple Ce3+ doped whitlockite phosphor: Synthesis, crystal structure, and photoluminescence properties

At present, the rare earth (RE) ions doped phosphors have attracted more and more attention because of their excellent properties. In this paper, a series of novel blue-purple β-Ca3(PO4)2:Ce3+ phosphors were synthesized by a high temperature solid phase method. The X-ray diffraction (XRD), infrared spectrum, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence excitation and emission spectra were used to investigate the crystal structure, composition and the luminescent properties of the resulting samples. The phosphor shows a strong absorption in the ultraviolet band. Under the excitation of 269 nm, the phosphor emits a strong purple fluorescence ranging from 360 to 520 nm. When Ce3+ doping content is 0.07 mol, the strongest luminescence intensity is reached, and the concentration quenching mechanism is dipole-dipole (d-d) interaction for Ce3+ based on Dexter theory.

A perovskite-like LaSrGaO4:Mn2+, Nd3+, Yb3+ NIR luminescent material for fluorescent temperature sensor

A NIR phosphor of the Mn2+, Nd3+, Yb3+ ions doped perovskite-like host LaSrGaO4 is successfully synthesized by high temperature solid phase method, and the energy transfer process about them is analyzed in detail. By measuring the temperature spectra of different samples and calculating the temperature sensitivities, it is found that the temperature sensitivity can be improved by adding Mn2+ and Yb3+ into LaSrGaO4:Nd3+, and that the maximum absolute sensitivity can be 5.64321%/K and that the relative sensitivity can be maintained at 0.474%/K. This NIR luminescent material LaSrGaO4:Mn2+, Nd3+, Yb3+ can be used as the NIR fluorescent temperature sensor for biological detection. In addition, the wide excitation bands of Mn2+, Nd3+ in visible region match well with the solar spectrum (AM 1.5), and the wide emission bands of Nd3+, Yb3+ in near infrared 900–1100 nm region are located in the spectral response curve of c-Si solar cells, so NIR luminescent material LaSrGaO4:Mn2+, Nd3+, Yb3+ may have the potential application in the spectral converter of c-Si solar cells to improve the conversion efficiency.

Synthesis and Luminescence Properties of SrGd2O4:Eu3+ Red Phosphors

As one of the important raw materials for LED products, phosphors play an important role. At present, the spectrum of LED phosphors lacks red light, resulting in poor quality of white LED products and a low color rendering index (Ra <80), which affects lighting effects. To solve this problem, we synthesized the SrGd2O4:Eu3+ red phosphor by a high-temperature solid-phase method. The structure and luminescence properties of SrGd2O4:Eu3+ red phosphors were studied by means of X-ray diffraction (XRD) measurements of their emission and excitation spectra, and their spectra were analyzed. We also studied the Eu3+ doping concentration with the best luminous efficiency and the color coordinate of the SrGd2O4:Eu3+ phosphor. The experimental results show that SrGd2O4:Eu3+ is a new red phosphor material that can be used for near-ultraviolet or blue-light excitation and has good practicability.

Enhancement of luminescence properties of SrAl2Si2O8: Eu3+ red phosphor

Aluminosilicate phosphors have been widely used in the fields of fluorescence and laser technology due to its excellent optical properties. However, red phosphors have low luminescence efficiency, and poor physicochemical stability, which cannot achieve efficient white light emission. Therefore, improving the luminescence performance of aluminosilicate red phosphors is a research hotspot in white LED. In this work, SrAl2Si2O8: Eu3+ red phosphor was synthesized by high temperature solid-phase method. By introducing charge compensator and flux, the luminescence intensity of the phosphor is increased. The best charge compensator is determined as Li+ with the same Eu3+ doping content. The best flux is H3BO3, and the optimal doping concentration of flux is 3 wt%. For SrAl2Si2O8: Eu3+, Li+, H3BO3 red phosphor, the CIE coordinates are (0.619, 0.380) and CCT is 3417 K, which is very close to the standard red light. Through LED packaging mixing phosphor with YAG: Ce3+, the method can significantly improve the color rendering index of WLED, up to 84.7. When the temperature reaches 150 °C, the luminescence intensity decreases to 88.02% of the initial value, which indicates that the SrAl2Si2O8 phosphor is an excellent stable red luminescent material.

Synthetic process and luminescence properties of Er3+, Yb3+ doping fluoride-based up-conversion phosphors

Fluoride-based doped Er3+, Yb3+ up-conversion (UC) luminescent materials were prepared via a traditional high-temperature solid-phase method. The optimum sintering temperature and holding time of phosphors were 625 °C and 1.5 h, respectively. When the molar ratio of Er3+/Yb3+ is 1:9, the phosphor shows the highest luminescence intensity. Simultaneously, NaF is used as the charge compensator and flux, which has vital effects on the luminescent properties; when the doping amount is 15 at.%, the luminescence intensity reached a maximum. The UC emission spectra of samples compose with three emitting peaks under the excitation of a 980 nm laser, including two green color-emitting peaks with a strong emission at 540 nm and a weaker emission at 521 nm and a red color emitting peak at 651 nm corresponding to the 4S3/2 → 4I15/2, 2H11/2 → 4I15/2, and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. The optimal CIE coordinate of the phosphor is (0.2925, 0.6896). These results indicate that solid solution green UC phosphors with higher purity was synthesized. These results indicate that due to the excellent physical and chemical stability of fluoride-based doped Er3+, Yb3+ solid solution up-conversion phosphors, it may have potential applications in display devices, optical communications, and biosensors.

Preparation and Properties of Cr3+ Doped Mg0.388Al2.408O4 Red Phosphor

The Cr3+ activated Mg0.388Al2.408O4 phosphor was synthesized by sol-gel and high temperature solid phase method in the air at 1400°C for 6h. The phosphors structure was measured by X-ray diffraction (XRD); excitation spectra, emission spectra and decay lifetime were obtained by fluorescence spectrophotometer equipped. It showed that the sample has two strong broad absorption ranging from 390nm to 420nm and 530nm to 590nm, and the peak positions are around 407nm and 552nm; the maximum of the red emission which is due to the transition from the 2Eg(2G) excited state to the 4A2g ground state is at 688 nm. And the lifetime of Cr3+ in the Mg0.388Al2.408O4 host is 4.8255ms.