Ca2+‐Doped LaCrO3: A Novel Energy‐Saving Material with High Infrared Emissivity

The present study describes the successful synthesis of a Ca²⁺‐doped LaCrO₃ ceramic with high infrared (IR) emissivity, which is important for high‐temperature applications for significant energy saving. It is demonstrated that 20 mol% Ca²⁺‐doped LaCrO₃, i.e., La_0.8Ca_0.2CrO₃, exhibited an IR emissivity as high as 0.95 in the spectral region of 3–5 μm, which was 33.8% higher than that of LaCrO₃. By using La_0.8Ca_0.2CrO₃ as IR radiation agent in surface coating of heating unit, the radiative heat transfer could be enhanced significantly. The mechanism of the high IR emissivity of La_0.8Ca_0.2CrO₃ was attributed to the following aspects: Ca²⁺ doping introduced an impurity energy level of Cr⁴⁺ into LaCrO₃ and increased the hole carrier concentration, enhancing both impurity absorption and hole carrier absorption in the IR region; moreover, the doping caused lattice distortion enhanced the lattice vibration absorption. This novel high IR emissivity ceramic shows a promising future in high‐temperature applications for the purpose of energy‐saving.     

Synthesis,Crystal Structure,and Enhanced Luminescence of Garnet‐Type Ca3Ga2Ge3O12:Cr3+ by Codoping Bi3+

Garnet‐type compound Ca₃Ga₂Ge₃O₁₂ and Cr³⁺‐doped or Cr³⁺/Bi³⁺ codped Ca₃Ga₂Ge₃O₁₂ phosphors were prepared by a solid‐state reaction. The crystal structure of Ca₃Ga₂Ge₃O₁₂ host was studied by X‐ray diffraction (XRD) analysis and further determined by the Rietveld refinement. Near‐infrared (NIR) photoluminescence (PL) and long‐lasting phosphorescence (LLP) emission can be observed from the Cr³⁺‐doped Ca₃Ga₂Ge₃O₁₂ sample, and the enhanced NIR PL emission intensity and LLP decay time can be realized in Cr³⁺/Bi³⁺ codped samples. The optimum concentration of Cr³⁺ in Ca₃Ga₂Ge₃O₁₂ phosphor was about 6 mol%, and optimum Bi³⁺ concentration induced the energy‐transfer (ET) process between Bi³⁺ and Cr³⁺ ions was about 30 mol%. Under different excitation wavelength from 280 to 453 nm, all the samples exhibit a broadband emission peaking at 739 nm and the intensity of NIR emission increases owing to the ET behavior from Bi³⁺ to Cr³⁺ ions. The critical ET distance has been calculated by the concentration‐quenching method. The thermally stable luminescence properties were also studied and the introduction of Bi³⁺ can also improve the thermal stability of the NIR emission.     

Preparation of environmentally friendly high-emissivity Ca2+-Fe3+ co-doped LaAlO3 ceramic

Ca²⁺-Cr³⁺ co-doped LaAlO₃ is an excellent ceramic material with high emissivity; however, it is harmful to the environment because of the presence of Cr³⁺ ions. In this study, Ca²⁺-Fe³⁺ co-doped LaAlO₃ ceramic materials were successfully prepared via a high-temperature solid-state reaction. The emissivity of Ca²⁺-Fe³⁺ co-doped LaAlO₃ was 0.91, which is approximately equal to that of Ca²⁺-Cr³⁺ co-doped LaAlO₃. To compensate for the lack of data on the thermophysical properties of doped LaAlO₃ high-emissivity ceramics, the thermal expansion coefficients and thermal conductivities of LaAlO₃ doped with Ca²⁺-Fe³⁺ or Ca²⁺-Cr³⁺ were investigated. The thermal conductivities of La_0.9Ca_0.1Al_0.9Fe_0.1O₃ and La_0.9Ca_0.1Al_0.9Cr_0.1O₃ at 1200°C were 3.802 and 3.707 W·m⁻¹·K⁻¹, respectively. The thermal expansion coefficients of La_0.9Ca_0.1Al_0.9Fe_0.1O₃ and La_0.9Ca_0.1Al_0.9Cr_0.1O₃ at 1200°C were 11.49×10⁻⁶ and 11.41×10⁻⁶ K⁻¹, respectively. These results indicate that Ca²⁺-Fe³⁺ co-doped LaAlO₃ exhibits great potential as a new generation of environmentally friendly near-infrared radiating materials in the field of energy efficiency.     

High Nd3+→Yb3+ energy transfer efficiency in tungsten‐tellurite glass: A promising converter for solar cells

This work reports on the energy transfer efficiency for Nd³⁺/Yb³⁺ co‐doped tellurite glasses (80TO₂‐20WO₃, in mol%,). The correlation between Yb³⁺ ion concentration and the downconversion mechanism was investigated using optical and thermal lens spectroscopies, which enabled investigation of the radiative and nonradiative processes, respectively, involved in energy transfer from neodymium to ytterbium. The Nd³⁺ near‐infrared fluorescence disappeared almost entirely when the maximum concentration of Yb³⁺ ions (4 mol%) was doped into the host. In contrast, there was a corresponding increase in the ytterbium emission at around 980 nm. When ytterbium was added, there was also a simultaneous reduction in the amount of heat generated by the sample due to a reduction in the nonradiative decay rate, corroborating the suspected high energy transfer efficiency of Nd³⁺→Yb³⁺. The results indicate that tungsten‐tellurite glasses may be of potential use in solar cells for matching the solar emission spectrum to the semiconductor cell.     

Preparation of infrared high radiation coatings from modified spinel NiFe2O4 and its energy saving applications

The NiFe spinel material itself has good thermal stability and emissivity and can be prepared as an infrared high radiation coating for energy saving applications in industrial high temperature furnace applications. In this study, Cr³⁺ and Cu²⁺ doped spinel NiFe₂O₄ was prepared by solid phase reaction at 1250 °C for 3 h and the microstructure and physicochemical properties of the powder and coating were characterised by XRD, SEM, EDS and IR radiometry. The effect of Cr³⁺ and Cu²⁺ doping on the infrared emissivity of spinel NiFe₂O₄ was investigated and energy saving assessment was carried out in a resistance furnace. The results show that the doping of Cr³⁺ and Cu²⁺ can significantly affect the emissivity of spinel powders in the 2.5–10 μm band, and the coatings prepared from the four powders have an emissivity of up to 0.95 in the 2.5–10 μm band. using this high temperature infrared radiation energy saving coating in a resistance furnace resulted in significant energy savings compared to no coating. The furnace was tested for energy saving by holding the furnace for 2 h and 5 h, and the energy saving efficiency reached 20.7% and 17.0% respectively. The coating was subjected to 10 thermal shock tests from room temperature to 700 °C. The coating bonded well and had good thermal shock resistance. Therefore, the coating has wide application prospects for energy saving applications in the field of industrial high temperature furnaces.     

Effects of Ca2+-Sr2+ doping on the infrared emissivity of LaCrO3

LaCrO₃ shows excellent thermal stability and good emissivity, and can be used as a potential thermal protection material for hypersonic vehicle. In this study, LaCrO₃ and Ca²⁺-Sr²⁺ doped LaCrO₃ were prepared by solid state reaction at 1400 °C for 2 h. The microstructures of the samples and effects of Ca²⁺-Sr²⁺ doping on the infrared emissivity of LaCrO₃ were studied by XRD, XPS, FT-IR, and UV–VIS–NIR spectrophotometer. The results show that after doping Ca²⁺ and Sr²⁺ ions, the infrared emissivity of all samples has significantly improved at 2.5–10 μm, from 0.61 (minimum value) to above 0.90. In the range of 10–14 μm, the emissivity of pure LaCrO₃ and La_0.8Ca_xSr_0.2-xCrO₃ samples shows a similar trend and all remains above 0.97. Therefore, doping Ca²⁺ and Sr²⁺ can significantly increase the emissivity of LaCrO₃ at 2.5–10 μm, which makes it have a wider application prospect in the field of high temperature thermal protection.     

Enhanced Sunlight Excited 1‐μm Emission in Cr3+–Yb3+ Codoped Transparent Glass‐Ceramics Containing Y3Al5O12 Nanocrystals

Cr³⁺–Yb³⁺ codoped transparent glass‐ceramics containing Y₃Al₅O₁₂ nanocrystals were prepared by heat treatment of as‐prepared glass sample and characterized by X‐ray diffraction and transmission electron microscopy. The efficient energy transfer from Cr³⁺ to Yb³⁺ ions through multi‐phonon‐assisted process was confirmed by the luminescence spectrum and fluorescent lifetime measurements. When excited by the lights from a solar simulator in the wavelength region of 400–800 nm, greatly enhanced near‐infrared emission around 1 μm was achieved from Cr³⁺–Yb³⁺ codoped glass ceramic compared with that from as‐prepared glass and Ce³⁺–Yb³⁺ codoped glass ceramic. These results demonstrate that the Cr³⁺–Yb³⁺ codoped glass ceramic is a promising material for enhancement of the efficiency of solar energy utilization.     

The effect of Mg2+ doping on the infrared emissivity of LaCrO3 perovskites

The infrared high emissivity ceramic material plays an important role in thermal protection of hypersonic vehicles. LaCrO₃, characterized by excellent thermal stability and high emissivity, can be applied as infrared high emissivity material. LaCrO₃ and Mg²⁺ doped LaCrO₃ were prepared via solid state reaction method. XRD analyses showed that LaCr_1-xMg_xO₃ (x = 0, 0.1, 0.2, 0.25, 0.3) were single-phase solid solutions. The doping-effect of Mg²⁺ on the infrared emissivity was investigated. In the range of 2.5–8 μm, the infrared emissivity of all doped materials had significant improvement, the average emissivity of materials increased from 0.66 to 0.83. In the range above 8 μm, the emissivity of all materials had a similar trend and compared to LaCrO₃, the emissivity of Mg²⁺ doped LaCrO₃ had little decrease.     

Cr3+‐activated Li5Zn8Al5Ge9O36: A near‐infrared long‐afterglow phosphor

Near‐infrared long‐afterglow (LAG) materials have attracted considerable attention owing to their high potential for in vivo imaging applications. Here, we present a series of near‐infrared LAG phosphors Li₅Zn₈Al_5?xGe₉O₃₆:xCr³⁺ (LZAG:Cr³⁺), which were synthesized using a solid‐state reaction method. The pure LZAG host exhibits blue photoluminescence and LAG emission. We investigated the effect of the zinc vacancy contents on the photoluminescence and LAG performance by adjusting the zinc content and introducing Ga³⁺ ions to substitute the Zn²⁺ sites in LZAG host. When Cr³⁺ ions were introduced into the LZAG host, LZAG:Cr³⁺ produced a strong, broad blue emission band centered at 456 nm and a near‐infrared emission band at 700 nm caused by the ²E → ⁴A₂ transition of Cr³⁺. The energy transfer processes from the LZAG host to Cr³⁺ were identified in the photoluminescence and LAG process. After irradiation at 258 nm for 10 minutes, the LAG emission of LZAG:0.008Cr³⁺ can last nearly 2.5 hours. Moreover, the LAG intensity and duration of LZAG: 0.008Cr³⁺ were significantly improved by introducing a small dose of Ga³⁺ ions. Finally, the traps and mechanism of LAG in LZAG, LZAG:Ga³⁺, and LZAG:Cr³⁺ were discussed in detail.     

Photoluminescence Properties of Color‐Tunable Ca3La6(SiO4)6: Ce3+, Tb3+ Phosphors

A series of newly developed color‐tunable Ca₃La₆(SiO₄)₆: Ce³⁺, Tb³⁺ phosphors were successfully prepared in this study. The crystal structures of the prepared phosphors were revealed to be hexagonal with space group P6₃/m, and the lattice parameters were evaluated via utilizing the Rietveld refinement method. Upon excitation at 288 nm, the emission spectra of Ce³⁺and Tb³⁺ ions co‐doped Ca₃La₆(SiO₄)₆ phosphors included a blue emission band and several emission lines. The blue emission band with a peak at 420 nm originated in the f–d transitions of Ce³⁺ ions, and the emission lines in the range of 450–650 nm were assigned to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ ions. Increasing the doping content of Tb³⁺ ions considerably strengthened Tb³⁺ emission and reduced Ce³⁺ emission owing to the energy transfer from Ce³⁺ to Tb³⁺ ions. The mechanism of the energy transfer was confirmed to be a dipole–dipole interaction. The effective energy transfer from Ce³⁺ to Tb³⁺ ions caused a color shift from purplish‐blue to yellowish‐green. Color‐tunable Ca₃La₆(SiO₄)₆: Ce³⁺, Tb³⁺ phosphors have the potential to be utilized in light‐emitting diodes with proper modulation of the amount of Tb³⁺ ions.     

Synthesis and luminescence properties of single‐component Ca5(PO4)3F:Dy3+, Eu3+ white‐emitting phosphors

A series of Ca₅(PO₄)₃F:Dy³⁺, Eu³⁺ phosphors was synthesized by a solid‐state reaction method. The XRD results show that all as‐prepared Ca₅(PO₄)₃F:Dy³⁺, Eu³⁺ samples match well with the standard Ca₅(PO₄)₃F structure and the doped Dy³⁺ and Eu³⁺ ions have no effect on the crystal structure. Under near‐ultraviolet excitation, Dy³⁺ doped Ca₅(PO₄)₃F phosphor shows blue (486 nm) and yellow (579 nm) emissions, which correspond to ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions respectively. Eu³⁺ co‐doped Ca₅(PO₄)₃F:Dy³⁺ phosphor shows the additional red emission of Eu³⁺ at 631 nm, and an improved color rendering index. The chromaticity coordinates of Ca₅(PO₄)₃F:Dy³⁺, Eu³⁺ phosphors also indicate the excellent warm white emission characteristics and low correlated color temperature. Overall, these results suggest that the Ca₅(PO₄)₃F:Dy³⁺, Eu³⁺ phosphors have potential applications in warm white light‐emitting diodes as single‐component phosphor.     

Structural insights in Dy3+‐doped β‐Tricalcium phosphate and its multimodal imaging characteristics

A series of Dysprosium (Dy³⁺) doped β‐Tricalcium phosphate [β‐TCP, β‐Ca₃(PO₄)₂] were developed for applications in magnetic resonance imaging (MRI) and computed tomography (CT). Characterization studies confirmed the Dy³⁺ occupancy at Ca²⁺(1), Ca²⁺(2), and Ca²⁺(3) lattice sites of β‐Ca₃(PO₄)₂ and its substitution limit was determined as 4.35 mol%. The transitions from the ⁶H_15/2 ground state to various excited energy levels is validated by the characteristic absorption peaks of Dy³⁺. Luminescence studies inferred two intense bands at 480 and 572 nm due to ⁴F_9/2→⁶H_15/2 (blue) and ⁴F_9/2→⁶H_13/2 (yellow) transitions of Dy³⁺. The paramagnetic and nontoxic behavior of Dy³⁺‐doped β‐Ca₃(PO₄)₂ were confirmed from magnetic and MTT tests, respectively. Dy³⁺ in the host induces a high X‐ray absorption ability for X‐ray computed tomography (CT) and showed efficient contrast T₂‐enhancing modality. Thus the proposed system could be used as a promising probe for multimodality with optical imaging, computed tomography and magnetic resonance imaging.     

Optical Property of Dy3+‐and Ce3+‐Doped Si–B–Na–Sr Glasses

Novel Dy³⁺ and Ce³⁺ doped Si–B–Na–Sr (SBNS) glasses were synthesized by melt‐quenching technique. Excited by 327 nm, the 0.5Dy³⁺‐and 0.5Ce³⁺‐doped SBNS exhibits white emission with Commission Internationale de L'Eclairage coordinates of (0.308, 0.280). Basic optical characterizations have been performed by measuring the absorption and emission spectra and calculating Judd–Ofelt intensity parameters, radiative probability, luminescence branching ratio, cross sections, and effective bandwidth. The Judd–Ofelt parameters Ω₂, Ω₄, and Ω₆ indicate a high asymmetrical environment and covalent environment in the optical glass. The emission color of Ce³⁺ and Dy³⁺ codoped transparent glass can be tuned from blue to white through energy transfer from Ce³⁺ to Dy³⁺ ions. The resulting glass may have potential application in white‐light‐emitting source.     

Optical Temperature Sensing Behavior of High‐Efficiency Upconversion: Er3+–Yb3+ Co‐Doped NaY(MoO4)2 Phosphor

A class of Yb³⁺/Er³⁺ co‐doped NaY(MoO₄)₂ upconversion (UC) phosphors have been successfully synthesized by a facile hydrothermal route with further calcination. The structural properties and the phase composition of the samples were characterized by X‐ray diffraction (XRD). The UC luminescence properties of Yb³⁺/Er³⁺ co‐doped NaY(MoO₄)₂ were investigated in detail. Concentration‐dependent studies revealed that the optimal composition was realized for a 2% Er³⁺ and 10% Yb³⁺‐doping concentration. Two‐photon excitation UC mechanism further illustrated that the green enhancement arised from a novel energy‐transfer (ET) pathway which entailed a strong ground‐state absorption of Yb³⁺ ions and the excited state absorption of Yb³⁺–MoO₄^2? dimers, followed by an effective energy transfer to the high‐energy state of Er³⁺ ions. We have also studied the thermal properties of UC emissions between 303 and 523 K for the optical thermometry behavior under a 980 nm laser diode excitation for the first time. The higher sensitivity for temperature measurement could be obtained compared to the previous reported rare‐earth ions fluorescence based optical temperature sensors. These results indicated that the present sample was a promising candidate for optical temperature sensors with high sensitivity.     

Environmental influence of high Na2O additions on microstructure and ligand field parameters of Cr3+ inside borosilicate glass

A glass system based on the Na₂O/B₂O₃-doped CrO₃ borosilicate has been prepared by the melt quenching technique. The structure, color, optical absorbance and ligand field parameters were investigated for a wide range of Na₂O additives (20–60 mol%). All X-ray photoelectron spectroscopy (XPS) profiles were used to study the chemical shift states of the glass-constituting elements. Fourier transform infrared (FTIR) analyses explored the internal structure and subnetwork units. Furthermore, from the FTIR results, we concluded the transformation of trigonal borate units (BO₃) to tetrahedral borate units (BO₄) and the possibility of transformation from B₃-O-Si linkages to B₄-O-Si linkages. Despite the fixed CrO₃ content, the doped glasses showed a color transition from green to yellow with additional Na₂O content. The increased intensity of the band at 451–427 nm and the decreased intensity of the band at 619–627 nm are the main reasons for this color transformation. The optical absorption spectra confirmed the existence of Cr³⁺ and Cr⁶⁺ states. A decreasing behavior for the crystal field splitting (10Dq) and an increasing behavior for Racah parameter (B) were obtained with further Na₂O additives. The decreasing behavior of 10Dq was attributed to reduced oxygen concentrations with more Na₂O/B₂O₃ substitutions. The increasing behavior of B reflects the tendency of the bond between the Cr cations and their oxygen ligands towards an ionic nature. Moreover, the Dq/B values indicated that Cr³⁺ cations are in high-field positions for the glass sample containing 20 mol% Na₂O, and Cr³⁺ cations are in intermediate field positions for the glass sample containing 30 mol% Na₂O. However, for the glass samples doped with 40, 50 and 60 mol% Na₂O glass samples, Cr³⁺-cations are in weak field positions. These results of (Dq/B) recommend the glass sample doped with 20 mol% Na₂O for tunable laser applications.     

Infrared radiation performance and calculation of B-site doped lanthanum aluminate from first principles

Pure LaAlO₃ and LaAl_1-xNi_xO₃ samples (x?=?0.05, 0.1, 0.15, 0.2, 0.25, 0.3) were prepared using a sol-gel technique. The samples were analyzed and characterized using XRD, SEM, FT-IR and XPS. The results showed that the infrared emissivity of LaAl_1-xNi_xO₃ powder prepared at 1500?℃ for 2?h increases with Ni²⁺ doping content. For x?=?0.25, the mean emissivity in the 3–5?µm infrared spectral region was 0.835. This was a 142% increase compared with that of pure LaAlO₃ (0.345). The doped Ni ions mainly exist with valences of +?2 and +?3 in the LaAlO₃ lattice. After doping, the concentration of electron holes and oxygen vacancies increased, leading to an enhancement of free carrier absorption in the system. It indicated that the Ni²⁺ doping would introduce an impurity energy level in the forbidden band of LaAlO₃ by first principles calculation, forming primarily by the hybridization of the 3d orbital electrons of the Ni ions and the 2p orbital electrons of the oxygen atoms. When x?=?0.25, the band gap decreased from 3.50?eV to 0.77?eV. The impurity energy level allows for a reduction in the energy required for the electrons transferring from the valence band to the conduction band, causing increased numbers of electron transitions between the band gaps, thus enhancing free carrier absorption and increasing the infrared emissivity of the material. The LaAl_1-xNi_xO₃ oxide materials prepared in this work had excellent infrared radiation properties. As a lining material at high temperature reacting furnace, the energy loss could be reduced, the heat utilization efficiency would be greatly improved, and the utility model could be used in the field of high-temperature thermal energy saving.     

Far‐Red‐Emitting BiOCl:Eu3+ Phosphor with Excellent Broadband NUV‐Excitation for White‐Light‐Emitting Diodes

Rare‐earth ion‐doped semiconducting phosphor has attracted extensive attention due to the ability to achieve efficient luminescence through the host sensitization. Here, we present a new type red‐emitting Eu³⁺ ‐doped BiOCl phosphors possessing a broad excitation band in the near‐ultraviolet (NUV) region. Experimental measurements and theoretical calculations confirm that Eu³⁺ ion dopants result in forming impurity energy level near valence band, and the excellent broadband NUV‐exciting ability of Eu³⁺ ion is due to the electronic transitions of BiOCl band gap. Moreover, the highest emission intensity of the phosphors is from the ⁵D₀ → ⁷F₄ transition of Eu³⁺ around 699 nm (far‐red) through whether host excitation or direct Eu³⁺ ions excitation, which lie in the particular structure of BiOCl crystals. Our results indicate that the Eu³⁺ ‐doped BiOCl crystals show great potential as red phosphors for white‐light‐emitting diodes.     

Luminescence and Quantum Efficiencies of Eu3+‐Doped Vanadate Garnets

Nondoped and 5.0 mol% Eu³⁺‐doped vanadate garnets Ca₅Mg₄(VO₄)₆, NaCa₂Mg₂[VO₄]₃, KCa₂Mg₂[VO₄]₃, and NaSr₂Mg₂[VO₄]₃ were synthesized by solid‐state reactions. The formation of single‐phase compound with garnet structure is confirmed by X‐ray diffraction. The photoluminescence (PL) and PL excitation (PLE) spectra are investigated together with color coordinates. The luminescence process is discussed on the charge‐transfer transitions in [VO₄]^3? ions and the crystal structure. The PL quantum efficiencies (QE) are measured for nondoped and Eu³⁺‐doped samples. The Eu³⁺‐doped samples have higher QEs than the corresponding nondoped ones although the energy transfer occurs from [VO₄]^3? to Eu³⁺. Broad emission band due to [VO₄]^3? with intense sharp lines due to Eu³⁺, which gives white color, is observed in Eu³⁺‐doped NaCa₂Mg₂[VO₄]₃ and NaSr₂Mg₂[VO₄]₃ under excitation with UV light. These materials are suggested to be useful for lighting under the excitation with near‐UV LED.     

Hydrothermal formation and up‐conversion luminescence of Er3+‐doped GdNbO4

The effect of concentration of Er³⁺ on the up‐conversion and photoluminescence properties of Gd_1.00?xEr_xNbO₄, x=0‐0.50 which has monoclinic fergusonite‐type structure as a main phase has been investigated, using a processing technique based on hydrothermal method. Under weakly basic hydrothermal condition at 240°C for 5 hours, a single phase of fergusonite‐type Gd_1.00?xEr_xNbO₄ solid solution was directly formed as nanocrystals by the substitutional incorporation of Er³⁺ into GdNbO₄ because of the gradual and linear decrease in the lattice parameters of the monoclinic phase corresponding to the Vegard's Law. The gadolinium niobate doped with 2 mol% Er³⁺, Gd_0.98Er_0.02NbO₄ after heating at 1300°C for 1 hour, which has nanocrystalline structure whose crystallite size is around 29 nm, exhibits the highest photoluminescence intensity in the green spectral region, 515‐560 nm under excitation at wavelength of 254 nm. On the other hand, the up‐converted luminescence intensity of the niobate nanocrystals becomes the maximum at the concentration of 20 mol% Er³⁺, Gd_0.80Er_0.20NbO₄ under excitation at 980 nm. These results demonstrate that the material, Er³⁺‐doped GdNbO₄ nanocrystals prepared through hydrothermal route and postheating has potential for up‐converting phosphor.     

Tailorable Multicolor Up‐conversion Emissions in Tm3+/Ho3+/Yb3+ Co‐Doped LiLa(MoO4)2

Using a modified sol–gel method, LiLa(MoO₄)₂: Tm³⁺/Ho³⁺/Yb³⁺ phosphors with tailorable up‐conversion (UC) emission colors were prepared. Under the excitation of a 980 nm laser diode, up‐conversion red and green emissions in Ho³⁺/Yb³⁺ co‐doped and blue emission in Tm³⁺/Yb³⁺ co‐doped LiLa(MoO₄)₂ were observed, respectively. The intensities of the RGB (red, green, and blue) emissions could be controlled by varying concentrations of Tm³⁺ or Ho³⁺, and the optimal composition was also determined. In Tm³⁺/Ho³⁺/Yb³⁺ co‐doped LiLa(MoO₄)₂, the UC emission colors could be tuned from blue through white to yellow by adjusting the concentrations of Tm³⁺ or Ho³⁺. The UC excitation mechanisms were also investigated based on the power dependence of UC luminescence intensity.