Photo- and cathodo-luminescence properties of (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors prepared by sol–gel method

Abstract

(Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors with different Ce³⁺ and Tb³⁺ contents were prepared by sol–gel method using citric acid as a chelating agent. The effects of Ce³⁺/Tb³⁺ doping concentration on the crystal structure and photo-/cathodo-luminescence properties of the phosphors were investigated. The X-ray diffraction analysis of the samples shows that the synthesized phosphors are well-crystallized and display a pure Lu₂O₃ phase, indicating the successful formation of (Lu, Gd)₂O₃ solid solution host. The phosphors show approximately spherical morphology, uniform distribution of particle size and elements. Upon the excitation of ultra-violet light, the photoluminescence spectra of the phosphors with different Ce³⁺ doping concentrations consist of four emission peaks, which correspond to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺ ions, respectively. The photoluminescence spectra of the phosphors with different Tb³⁺ doping concentrations consist of five emission peaks, which correspond to the ⁵D₃ → ⁷F₄ and ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺ ions, respectively. Upon the excitation of cathode ray, the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors exhibit luminescence spectra similar to that of the samples excited by ultra-violet light and a color-tunable luminescence property. In addition, the energy transfer mechanism between Ce³⁺ and Tb³⁺ ion is also discussed.

1 Introduction

Ce³⁺/Tb³⁺ doped phosphors have been extensively studied in recent years for their potential applications in three-base color white light-emitting diodes (w-LEDs), cathodoluminescence (CL) phosphors for field emission display (FED) applications, high energy laser technology, cathode-ray tubes (CRT), biological imaging, and so on [1,2,3,4,5,6,7,8]. Especially, in CL bio-imaging application of the phosphors, the size of an electron beam spot is on the order of nanometers, so by using suitable imaging probes, CL microscopy enables multicolor biological imaging with nanoscale spatial resolution [8]. Tb³⁺ ion is an important activator with 4f → 4f emission peak in the green spectrum region with high color purity centered at 543 nm, corresponding to ⁵D₄ → ⁷F₅ transition. However, due to the absolutely forbidden 4f → 4f electric dipole transition, the absorption transition of Tb³⁺ ion is very weak. Ce³⁺ ion possesses a strong broadband excitation in the near-ultraviolet (NUV) band due to the characteristics of optically allowed 4f → 5d transition from the ground state ²F_5/2 to 5d level. Using Ce³⁺ ion as a sensitizer in Tb³⁺-doped phosphors, an efficient energy transfer (ET) is possible between Ce³⁺ and Tb³⁺ ions and the photoluminescence intensity of the phosphors can be increased. Therefore, Ce³⁺ and Tb³⁺ co-doped phosphors have been widely investigated as the green-emitting phosphors because of the high luminescent efficiency upon the electron beam or ultraviolet (UV) light excitation [9,10,11,12].

Different types of host materials for Ce³⁺/Tb³⁺ doped phosphors have been studied. For example, fluoride hosts, including Ln³⁺:CeF₃ (Ln = Nd, Tb) used as bimodal probes for fluorescence and X-ray computed tomography (CT) [13], Sr₂ScF₇: Ce/Tb nanocrystals for lighting, photonic and biological imaging applications [14], β-Na(Gd, Lu)F₄:Ln³⁺ (Ln = Ce, Eu, Tb) nanoparticles for radio-luminescent materials [15]; Borate hosts, for example Ba₃Y₂B₆O₁₅:Ce³⁺/Tb³⁺ [16], Sr₃Lu₂(BO₃)₄: Ce³⁺/Tb³⁺ [17] phosphors for NUV-excited white LEDs, Dy³⁺/Ce³⁺/Tb³⁺-activated MgB₄O₇ phosphor for dosimetry application [18]; Aluminosilicate phosphor CaAl₂Si₂O₈: Ce/Tb/Yb for applications in Si-based solar cells as an efficient NUV to near-infrared (NIR) converters [19]; Phosphate phosphor SrMg₂(PO₄)₂: Ce³⁺, Tb³⁺ with tunable luminescence for LEDs devices [20]; And gadolinium oxysulfide phosphor Gd₂O₂S: Tb, which is used as an efficient X-ray-to-light converter in many medical imaging modalities [21].

Until now, there have been few reports about the photoluminescence (PL) and CL properties of Ce³⁺/Tb³⁺ co-doped phosphors using Lu₂O₃–Gd₂O₃ solid solution as host materials. Lutetium oxide (Lu₂O₃) has cubic crystalline structure, and is an attractive sesquioxide host for optical applications, including high-performance scintillation detector and laser gain media. Lu₂O₃ is photo-thermally and photo-chemically stable and has a wide range of optical transparency from visible to NIR regions. The remarkable advantage of Lu₂O₃ is its high density (9.43 g/cm³) along with high atomic number (Z = 71 for Lu), which gives Lu₂O₃ with high stopping power for ionizing radiation detection [22, 23]. Similar to Lu₂O₃, gadolinium oxide (Gd₂O₃) also possesses high density (7.407 g/cm³) and high Z-numbers (Z = 64 for Gd) and favorable physical properties, including high melting point, low thermal expansion, and lower phonon energy, and has been widely studied as the host of luminescent lanthanide (Ln³⁺) ions for optical application. The similar bixbyite cubic crystal structure of Lu₂O₃ and Gd₂O₃ and the close ionic radii of Lu³⁺ and Gd³⁺ ion make Lu₂O₃–Gd₂O₃ solid solution a promising phosphor host material with a wide range of applications. The large band gaps (5.4–5.5 eV) of Lu₂O₃ and Gd₂O₃ allow them to accommodate the energy levels of different luminescent activators, especially rare-earth ions [24,25,26]. Rétot et al. reported the investigation of the scintillation properties of Lu₂O₃: Eu³⁺ and (Lu_0.5Gd_0.5)₂O₃: Eu³⁺ sesquioxide ceramics. They found that compared with Lu₂O₃: Eu³⁺ ceramics, (Lu_0.5Gd_0.5)₂O₃: Eu³⁺ presented a faster intrinsic decay time for Eu³⁺ and showed a reduced afterglow over the hundreds of milliseconds time range and a reduced thermally stimulated luminescence (TSL) intensity over the 10–650 K temperature range, which can be applied as a potential new scintillator with improved time response characteristics [23]. Lu et al. demonstrated that Gd₂O₃: Eu phosphor showed stronger photoluminescence intensity compared with Lu₂O₃: Eu phosphor due to the low electronegativity of Gd³⁺, and Gd³⁺-doping in Lu₂O₃: Eu can enhance the PL efficiency of the phosphors [27]. Thus, studies of the preparation and luminescent properties of Ce³⁺/Tb³⁺ co-doped (Lu, Gd)₂O₃ phosphors are meaningful for expanding the applications of Ce³⁺/Tb³⁺ phosphors in the relevant fields. In this work, a series of Ce³⁺/Tb³⁺ co-doped (Lu, Gd)₂O₃ phosphors with were prepared by sol–gel method using citric acid as the chelating agent. The crystal structures and compositional effects of Ce³⁺/Tb³⁺ doping on the PL and CL properties of the phosphors were studied. The ET mechanism between Ce³⁺ and Tb³⁺ ions in the phosphors is also discussed.

2 Experimental procedures

In this work, two groups of (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphor samples were prepared according to the following chemical formulas, i.e., (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mol%) and (Lu_0.847−yGd_0.15Ce_0.003Tb_y)₂O₃ (y = 7, 8, 9, 10, 11, 12 and 13 mol%). Taking the sample of one chemical composition as an example, the experimental procedure is as follows: Stoichiometric amounts of Lu₂O₃, Gd₂O₃, CeO₂ and Tb₄O₇ were weighed according to the above chemical formulas and put in a beaker, then the nitric acid (HNO₃) solution (6 mol/L in concentration) was added into the beaker, which was then put on a magnetic stirrer and stirred at 80 °C for 4 h to form the transparent rare-earth (RE) nitrate solution. Citric acid (C₆H₈O₇), which acted as a chelating agent with amount of RE₂O₃: citric acid = 1:1.667 in molar ratio was added into the nitrate solution while the solution was stirred continuously until the homogeneous solution was formed. The beaker with the obtained solution was then put in a thermostat water bath and heated at 70 °C for 4 h to form the wet-gel precursor, which was then dried at 160 °C for 2 h to form the dry-gel. The obtained dry-gel was crushed in an agate mortar, and then calcined at 1000 °C for 2 h in reduction atmosphere to obtain the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphor sample. The corresponding schematic representation of the experimental procedure is shown in Fig. 1.

Fig. 1

Schematic representation of the experimental procedure

Phase identification of the phosphor samples was conducted by X-ray diffraction (XRD) analysis on a Rigaku Ultima IV diffractometer with CuKα radiation source to evaluate the crystalline structure of the samples. The morphology and element distribution of the phosphors were measured with a TESCAN scanning electron microscope (SEM) attached with an Energy-dispersive spectrometer (EDS, Oxford Instruments). PL and photoluminescence excitation (PLE) spectra of the phosphor samples were measured on a Hitachi F-7000 spectrophotometer with a 150 W xenon lamp as the excitation source. CL spectral of the phosphor samples were measured on a Hitachi F-7000 spectrophotometer coupled with an Optic-Zenith electron-beam-ray system as the excitation source. All the characterizations were conducted at room temperature.

3 Results and discussion

3.1 XRD patterns and morphology of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphor samples

Figure 2a shows the XRD patterns of the as-prepared (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphor samples with different Tb³⁺ doping concentrations. The patterns display that all the diffraction peaks of the phosphors are consistent with that of pure Lu₂O₃ phase (JCPDS No. 12-0728), no secondary phases or impurities are detected, indicating that Gd₂O₃ can incorporate well into Lu₂O₃ matrix to form the (Lu, Gd)₂O₃ solid solution host. Taking the diffraction peak of (222) crystallographic plane as a reference, it can be seen from the enlarged patterns of Fig. 2b that with the increase of Tb³⁺ doping concentration, the diffraction peaks of the samples shift slightly toward the lower diffraction angle. The ionic radii of the Lu³⁺, Gd³⁺, Ce³⁺ and Tb³⁺ ions are 0.848 Å, 0.938 Å, 1.034 Å and 0.923 Å, respectively. Partial substitution of Lu³⁺ ions by Gd³⁺, Ce³⁺ and Tb³⁺ ions in the Lu₂O₃ matrix can result in the expansion of unit cell and so the increase of interplanar spacing d. According to the Bragg's law 2dsinθ = λ, where d is the interplanar spacing, θ is the Bragg angle, λ is the incoming X-ray wavelength, the increase of d results in the decrease of θ. So, with the increase of Tb³⁺ doping concentrations, the diffraction peaks of the samples shift to the lower angles, which further verifies the successful consolidation of Gd³⁺, Ce³⁺ and Tb³⁺ ions into the Lu₂O₃ matrix. From the XRD analysis results in Fig. 2, the crystallite sizes of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphor samples with different Tb³⁺ doping contents are estimated by the Scherrer equation, D = 0.89λ/βcosθ, where D is the average crystallite size, λ is the x-ray wavelength, θ is the Bragg angle, β is the corrected full-width at half-maximum (FWHM) of the x-ray peak on the 2θ axis [28, 29]. The estimated crystallite sizes of the phosphors with different Tb³⁺ doping contents are between 70 and 82 nm. Figure 2c shows the SEM image of the phosphor sample with 10 mol% Tb³⁺ doping content, the particles of the phosphor show approximately spherical morphology and uniform particle size distribution, and the particle size is at nanoscale. Figure 3 displays the corresponding EDS mapping images of the RE elements in the sample, which indicates the uniform doping of Lu, Gd, Ce and Tb in the sample.

Fig. 2

a XRD patterns of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors with different Tb³⁺ doping concentrations; b enlarged XRD pattern between 29.3 and 29.8 degree; c SEM image of the phosphor

Fig. 3

EDS mapping images of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors

3.2 PL and CL spectral properties of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors

Figure 4 shows the PLE spectra of the (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors by monitoring the ⁵D₄ → ⁷F₅ emission of Tb³⁺ (λ_em = 543 nm). As shown in Fig. 4, there are strong excitation bands ranging from 240 to 350 nm with the highest intensity centered at 278 nm, which can be attributed to the 4f¹–4f⁰5d¹ transitions of Ce³⁺ ions. In addition, several very small peaks can be seen in the range of 350–400 nm, which could be attributed to the f-f transitions of Tb³⁺ ions. Due to the forbidden nature of these transitions, their oscillator strengths are much weaker than that of the spin-allowed 4f¹–4f⁰5d¹ transitions of Ce³⁺ ions, which reveals that Tb³⁺ ions are essentially excited by Ce³⁺ [30, 31]. The PL spectra of the (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors (λ_ex = 278 nm) are presented in Fig. 5a. All the samples show obvious PL emission peaks in the range of 450–650 nm, four emission peaks centered at 491, 543, 583 and 623 nm can be assigned to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺ ions, respectively [2, 11, 32]. Among the four emission bands, the green light emission at 543 nm, which corresponds to the ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions, has the strongest PL emission intensity. The positions and shapes of the PL emission peaks remain constant with the increase of Ce³⁺ ion doping concentration. Taking the PL intensity of 543 nm as a reference, Fig. 5b shows the PL intensities of the (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors at 543 nm as a function of Ce³⁺ doping concentration. The PL intensities of the phosphors increase firstly with the increase of Ce³⁺ concentrations, and reach the maximal value when the Ce³⁺ content is at 0.3 mol%, then decrease with the continuous increase of Ce³⁺ concentration, which may be attributed to the concentration quenching effect. Figure 5c displays the corresponding CIE chromaticity coordinate diagram of the samples. The CIE chromaticity coordinates of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mol% Ce³⁺-doped phosphors are (0.2587, 0.5819), (0.2554, 0.5776), (0.2573, 0.5801), (0.2595, 0.5826), (0.2657, 0.5848), and (0.2691, 0.5862), respectively. It can be seen that the variation of Ce³⁺ doping content has minor effect on the luminous color of the phosphors, the chromaticity coordinates of the phosphors are close to each other, all in the pure green light region, indicating the color-stability of the phosphors.

Fig. 4

PLE spectra of the (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors

Fig. 5

a PL spectra of the (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors (λ_ex = 278 nm); b PL intensity of Tb³⁺ (543 nm) as a function of Ce³⁺ doping concentration; c CIE chromaticity coordinate diagram

Figure 6 shows the PLE spectra of the (Lu_0.847-yGd_0.15Ce_0.003Tb_y)₂O₃ (y = 7–13 mol%) phosphors by monitoring the ⁵D₄ → ⁷F₅ emission of Tb³⁺ (λ_em = 543 nm). It can be seen from Fig. 6 that by monitoring 543 nm emission of Tb³⁺ ion, the PLE spectra exhibit three excitation bands, the band centered at 243 nm belongs to the 4f-5d transition of Tb³⁺, the wide band in the range of 260–330 nm can be attributed to the excitation transition of Ce³⁺, and the weak excitation band in the range of 340–400 nm belongs to the intra 4f⁸ excitation transition of Tb³⁺ [2, 10, 33]. Figure 7a displays the PL spectra of the (Lu_0.847-yGd_0.15Ce_0.003Tb_y)₂O₃ (y = 7–13 mol%) phosphors upon 243 nm excitation. The emission peaks at 468 nm can be assigned to the ⁵D₃ → ⁷F₄ transition of Tb³⁺ ion., and the peaks at 491, 543, 583 and 623 nm are due to transitions of ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺ ions, respectively [2, 9, 11, 32, 34]. Among the five emission peaks, the green emission at 543 nm (⁵D₄ → ⁷F₅) is predominant. Taking the PL intensity of 543 nm as a reference, it can be seen from Fig. 7b that with the increase of Tb³⁺ doping concentration, the PL intensities of the phosphors increase firstly and reach the maximal value when the doping concentration of Tb³⁺ is at 10 mol%, then decrease with the continuous increase of Tb³⁺ concentration. Figure 7c shows the corresponding CIE chromaticity coordinate diagram of the phosphors. The CIE chromaticity coordinates of 7, 8, 9, 10, 11, 12 and 13 mol% Tb³⁺-doped phosphors are (0.2467, 0.5408), (0.2516, 0.5509), (0.2406, 0.5374), (0.256, 0.5607), (0.255, 0.5605), (0.2505, 0.5352), and (0.2566, 0.5374), respectively. The phosphors also display a color-stability property upon the variation of Tb³⁺-doping concentration, the luminous color of the phosphors is all in the pure green light region, which is very important for the application of the synthesized samples as a green phosphor in the related fields.

Fig. 6

PLE spectra of the (Lu_0.847−yGd_0.15Ce_0.003Tb_y)₂O₃ (y = 7–13 mol%) phosphors

Fig. 7

a PL spectra of the (Lu_0.847−yGd_0.15Ce_0.003Tb_y)₂O₃ (y = 7–13 mol%) phosphors (λ_ex = 243 nm); b PL intensity of Tb³⁺ (543 nm) as a function of Tb³⁺ doping concentration; c CIE chromaticity coordinate diagram

The PL properties of (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors upon UV excitation are determined by transitions between f-electron and d-electron states of Ce³⁺ and between different f-electron states of Tb³⁺, which is schematically shown in Fig. 8. Upon UV excitation, electrons of Ce³⁺ in the 4f ground state are populated to the higher 5d excited state, and then relax to the lowest splitting 5d state non-radiatively. Some of the excited electrons come back to ²F_7/2/²F_5/2 levels and generate 5d-4f emission of Ce³⁺, other electrons relax non-radiatively to the 4f ground state and transfer the energy to Tb³⁺ by ET process to populate ⁵D₃ and ⁵D₄ levels of Tb³⁺. Subsequent radiative transitions between the excited ⁵D₄ state and the ⁷F_J (J = 0–6) ground states of Tb³⁺ generate strong green luminescence, and the emission ⁵D₄ → ⁷F₅ centered at 543 nm is predominant [1, 2, 11, 32]. Figure 9a shows the PL spectra of the (Lu_0.747Gd_0.15Ce_0.003Tb_0.1)₂O₃ phosphor sample upon 243 nm, 278 nm and 305 nm excitation. It is noted that the excitation wavelength does not change the location and shape of the emission bands, which means the energy level transitions of the PL emission processes are the same. Meanwhile, excitation wavelength has obvious influence on the PL emission intensity of the phosphor samples, the sample with 243 nm excitation has the strongest PL intensity. Figure 9b shows the corresponding CIE chromaticity coordinate diagram of the sample, the CIE chromaticity coordinates of 243 nm, 278 nm and 305 nm-excited sample are (0.256, 0.5607), (0.2512, 0.5295), and (0.2552, 0.5399), respectively. It can be seen that the change of excitation wavelength can slightly affect the luminous color of the phosphor, which generally shifts from green to green–blue region with the increase of excitation wavelength from 243 to 305 nm.

Fig. 8

Schematic diagram of energy transfer between Ce³⁺ and Tb³⁺

Fig. 9

a PL spectra of the (Lu_0.747Gd_0.15Ce_0.003Tb_0.1)₂O₃ phosphor upon excitation of different wavelength; b CIE chromaticity coordinate diagram

In addition to being excited by UV light, the as-prepared (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors can also be excited by cathode ray. Figure 10a illustrates the CL spectra of the synthesized (Lu_0.8-xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors upon the excitation of cathode ray (accelerating voltage = 12 kV). Upon the excitation of cathode ray, the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors exhibit a strong green emission, the CL emission bands of the phosphors are similar to that of the PL emission bands, indicating the similarity of the emission mechanism of the two luminescence modes [4, 35, 36]. The CL spectra of (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors consist of four emission bands, corresponding to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺, respectively, the ⁵D₄ → ⁷F₅ transition at 543 nm has the strongest emission intensity. Figure 10b shows the CL intensities of the (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors at 543 nm as a function of Ce³⁺ doping concentration. The CL intensities of the phosphors increase firstly with the increase of Ce³⁺ concentrations, and reach the maximal value when the Ce³⁺ content is at 0.4 mol%, then decrease with the continuous increase of Ce³⁺ concentration. The corresponding CIE chromaticity coordinate diagram of the phosphors is shown in Fig. 10c, the CIE chromaticity coordinates of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mol% Ce³⁺-doped phosphors are (0.3654, 0.5465), (0.356, 0.5535), (0.3305, 0.571), (0.3308, 0.571), (0.3299, 0.576), and (0.3704, 0.5425), respectively. It can be seen from Fig. 10c that upon the excitation of cathode ray, the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors demonstrate a color-tunable luminescence property. With the increase of Ce³⁺-doping concentration, the luminous color of the phosphors can be generally adjusted from yellow-green to pure green region, which is different from that of the UV-excited samples. The color-tunable CL property of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors reveals that the synthesized phosphors may be a promising material for the application in the relevant fields, for example in biological imaging and FED device applications [2, 4, 8].

Fig. 10

a CL spectra of the (Lu_0.8−xGd_0.15Ce_xTb_0.05)₂O₃ (x = 0.1–0.6 mol%) phosphors; b CL intensity of Tb³⁺ (543 nm) as a function of Ce³⁺ doping concentration; c CIE chromaticity coordinate diagram

4 Conclusions

A series of (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors were prepared by sol–gel method using citric acid as a chelating agent. The synthesized phosphors are well-crystallized and display a pure Lu₂O₃ phase, indicating the successful formation of (Lu, Gd)₂O₃ solid solution host. The SEM analysis indicate that the phosphors show approximately spherical morphology and uniform particle size distribution, and the particle size is at nanoscale. The EDS analysis indicates that the elements of Lu, Gd, Ce and Tb are doped uniformly into the phosphors. Upon the excitation of UV light, the PL spectra of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors with different Ce³⁺ doping contents consist of four emission peaks centered at 491, 543, 583 and 623 nm, which correspond to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transition of Tb³⁺ ions, respectively. The green light emission originating from the ⁵D₄ → ⁷F₅ transition (543 nm) has the strongest PL intensity. Taking the PL intensity of ⁵D₄ → ⁷F₅ transition as a reference, with the increase of Ce³⁺ concentration, the PL intensities of the phosphors increase firstly and reach the maximal value when the Ce³⁺ content is at 0.3 mol%, then decrease with the continuous increase of Ce³⁺ concentration. The PL spectra of the (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors with different Tb³⁺ doping contents consist of five emission peaks, the emission peaks at 468 nm can be assigned to the ⁵D₃ → ⁷F₄ transition of Tb³⁺ ion., and the peaks at 491, 543, 583 and 623 nm are due to transitions of ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transition of Tb³⁺ ions, respectively. Among the five emission peaks, the green emission at 543 nm (⁵D₄ → ⁷F₅) is predominant. With the increase of Tb³⁺ doping concentration, the PL intensities of the samples at 543 nm increase firstly and reach the maximal value when the doping content of Tb³⁺ is at 10 mol%, then decrease with the continuous increase of Tb³⁺ concentration. The (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors excited by cathode ray show luminescence spectra similar to that of the samples excited by UV light and a color-tunable luminescence property. The research results of the work indicate that the synthesized (Lu, Gd)₂O₃: Ce³⁺, Tb³⁺ phosphors have potential applications in the fields of three-base color w-LEDs, CL phosphors, FED devices, biological imaging, and so on..