Photoluminescence properties of Ba2LaSbO6:Mn4+ deep-red-emitting phosphor for plant growth LEDs

Photoluminescence properties of Ba2LaSbO6:Mn4+ deep-red-emitting phosphor for plant growth LEDs

Journal of Luminescence 209 (2019) 1–7 Contents lists available at ScienceDirect Journal of Luminescence journal homepage: www.elsevier.com/locate/j...

4MB Sizes 0 Downloads 4 Views

Journal of Luminescence 209 (2019) 1–7

Contents lists available at ScienceDirect

Journal of Luminescence journal homepage: www.elsevier.com/locate/jlumin

Photoluminescence properties of Ba2LaSbO6:Mn4+ deep-red-emitting phosphor for plant growth LEDs

T

Yongchun Ren, Renping cao , Tao Chen, Lei Su, Xinyu Cheng, Ting Chen, Siling Guo, Xiaoguang Yu ⁎

College of Mathematics and Physics, Jinggangshan University, Ji’an 343009, China

ARTICLE INFO

ABSTRACT

Keywords: Perovskites Phosphors Mn4+ ion Deep red emission Plant growth LEDs

In this work, Ba2LaSbO6:Mn4+ phosphors are prepared successfully in air by solid-state reaction method, which is confirmed by the X-ray powder diffractions patterns, decay curves, the time-resolved emission spectra and luminescence properties. Monitored at 678 nm, the excitation spectrum of Ba2LaSbO6:Mn4+ phosphor is observed in the range of 250–575 nm. Under the excitation of 380 nm, Ba2LaSbO6:Mn4+ phosphor exhibits strong deep-red emission in the range of 625–740 nm with emission peak at 678 nm due to the 2E → 4A2 transition of Mn4+ ion. The emission spectrum well matchs with the absorption spectrum of plants in the range of 625–740 nm. The temperature-dependent emission spectra illustrate the thermal stability of Ba2LaSbO6:Mn4+ phosphor and the thermal quenching mechanism is explained by the configuration coordinate of Mn4+ ion. The luminous mechanism of Ba2LaSbO6:Mn4+ phosphor is explained by the Tanabe-Sugano energy level diagram of Mn4+ ion. The experimental results show that the Ba2LaSbO6:Mn4+ deep-red-emitting phosphor would have potential application in plant growth LEDs.

1. Introduction With the population increase and the world economy development, the energy and environmental issues have attracted increasing attention. In order to obtain high-quality vegetables and green grains, the commercial artificial greenhouse planting technology has been attracted more interest in recent years [1–3]. Light is one of important roles during the process of plant growth, which can promote plants blooming or delay the plant blooming time. The blue (430–520 nm), red to deep-red (630–750 nm) light are responsible for photosynthesis, phototropism, and photomorphogenesis, respectively [4,5]. Under the artificial greenhouse planting environments, the plants can be exhibited optimal growth and enhanced the yield and quality by the effectively controlling and adjusting the light source with blue, red, and deep-red emissions. The traditional light sources (e.g., fluorescent lamp, incandescent lamp, and metal halide lamp etc) for plant illumination are being used less and less because of many shortcomings, such as the high energy consumption, the low growth efficiency, the environmental influence, the continuous composite lights with unadjusted spectrum, and the spectral mismatch between the absorption spectrum of plant and the emission spectrum of light sources [6–8]. The light-emitting diodes

(LEDs) as a new type of light source show many advantages, such as energy-savings, low radiant heat output, high efficiency, environmentfriendliness, and long life [9,10]. More importantly, the spectral composition of LEDs can be adjusted according to the needs for the growth of plants. According to the absorption spectrum properties of plants, the design of phosphors for LED plant growth lamp is mainly blue and red phosphors [11], however, phosphors with deep-red emission for plant growth are attracting many attentions. Therefore, the research on deepred-emitting phosphors is very meaningful. When the transition metal ion Mn4+ is stable in host including octahedral structure, Mn4+ can show strong broad absorption in the near ultraviolet (n-UV) and blue region due to the 4A2 → 4T1, 2T2, and 4T2 spin-allowed transitions of Mn4+ ion [12,13], and emits red or deep-red light because of the transition 2E → 4A2 of Mn4+ ion [14], which are significant for plant growth. Recently, there are some reports on Mn4+doped luminescence materials for the artificial greenhouse plants, such as La(MgTi)1/2O3:Mn4+ [2], Li2MgZrO4:Mn4+ [3], LiLaMgWO6:Mn4+ [4], La2LiSbO6:Mn4+ [15]. However, the practical application is unsatisfactory. So, the researches on novel Mn4+-doped luminescence materials for the artificial greenhouse plants are necessary. The doubleperovskites are being used as host materials for dopant because of the

Corresponding author. E-mail addresses: [email protected] (Y. Ren), [email protected] (R. cao), [email protected] (T. Chen), [email protected] (L. Su), [email protected] (X. Cheng), [email protected] (T. Chen), [email protected] (S. Guo), [email protected] (X. Yu). ⁎

https://doi.org/10.1016/j.jlumin.2019.01.014 Received 25 August 2018; Received in revised form 5 January 2019; Accepted 7 January 2019 Available online 14 January 2019 0022-2313/ © 2019 Elsevier B.V. All rights reserved.

Journal of Luminescence 209 (2019) 1–7

Y. Ren et al.

good thermal/chemical stability and physical properties. Mn4+-doped double-perovskites have been reported widely, such as Sr2ZnWO6:Mn4+ [16], AE2LaTaO6:Mn4+ (AE = Ca, Sr, and Ba) [17], Li2Mg3SnO6:Mn4+ [18], La2MgGeO6:Mn4+ [19], NaMgGdTeO6:Mn4+ [20], NaLaMgWO6:Mn4+ [21], Y2MgTiO6:Mn4+ [22]. Ba2LaSbO6 as one of double-perovskites contains two octahedral structure, [SbO6] and [LaO6] [23]. Up to now, Ba2LaSbO6:Mn4+ phosphor has not been reported. According to the ionic radius similarity mechanism, the [SbO6] octahedron in Ba2LaSbO6 can provide a good chance for the replacement of Mn4+ ion. In this work, Ba2LaSbO6:Mn4+ deep-red emitting phosphor is prepared in air by solid state reaction method. The crystal structures, luminescence properties, thermal stability, and decay curves of Ba2LaSbO6:Mn4+ phosphor are systematically studied. We research the influence of Mn4+ content to the emission intensity and lifetime of Ba2LaSbO6:Mn4+ phosphor. The time-resolved emission spectra and temperature-dependent emission spectra of Ba2LaSbO6:Mn4+ phosphor are measured and explained. The luminous mechanism of Ba2LaSbO6:Mn4+ phosphor is explained by the Tanabe-Sugano energy level diagram of Mn4+ ion.

Fig. 1. The unit cell of Ba2LaSbO6 drawn on the basis of ICSD #153136.

60 W is available to record the decay curves for lifetimes. The quantum efficiency (QE) is directly measured by the steady-state FLS980 spectrofluorimeter with an integrating sphere.

2. Experimental

3. Results and discussion

2.1. Synthesis process

The unit cell of Ba2LaSbO6 drawn on the basis of ICSD #153136 is presented in Fig. 1. The host (Ba2LaSbO6) has double-perovskite symmetry and the crystal phase belongs to trigonal system with the space group of R3̄(148). The lattice parameters are a = b = c = 6.0825(1) Å, V= 160.17(1) Å3, and Z = 1 [24]. In host (Ba2LaSbO6) crystal lattice, the La3+ and Sb5+ ions are coordinated by six oxygen atoms and form [SbO6] and [LaO6] octahedra, respectively. The Ba2+ ion is coordinated by three oxygen atoms and form [BaO3]. Ba2+ ions are located in the center of the gap between [SbO6] and [LaO6] octahedra. According to ionic radius similar principle (CN = 6, Ba2+: ~1.35 Å, La3+: ~1.03 Å, Sb5+: ~0.62 Å, and Mn4+: ~0.54 Å) [25], it can be confirmed that Mn4+ ions will replace the Sb5+ ion sites rather than La3+ ion in host (Ba2LaSbO6) lattice. There are different valence states between Sb5+ and Mn4+. In order to keep charge balance, electron hole (v-) may be formed, thus, the charge equilibrium relationship is Mn4+ → Sb5+ + v. XRD patterns of the joint committee powder diffraction standards (JCPDS) no. 54-958 (Ba2LaSbO6) and Ba2LaSb(1-x)O6:xMn4+ (x = 0.0, 0.2, 0.6, and 1.0 mol%) phosphors are displayed in Fig. 2. It can be well found that XRD patterns of Ba2LaSb(1-x)O6:xMn4+ (x = 0.0, 0.2, 0.6, and 1.0 mol%) phosphors are well in line with that of JCPDS no. 54-958 (Ba2LaSbO6). The XRD diffraction peaks of the other crystalline phases and raw materials are not observed. So, we confirm that all samples are a pure phase (Ba2LaSbO6). The experimental result indicates that the host (Ba2LaSbO6) crystal phase structure has not the significant change

In this work, a series of Ba2LaSb(1-x)O6:xMn4+ (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) phosphors are synthesized in air by the hightemperature solid-state reaction method according to the following chemical reaction equation.

4BaCO3 + La2O3 + (1 = 2Ba2LaSb(1

x )Sb2 O5 + 2xMnCO3 + 3x/2O2

x ) Mnx O6 + (4 + 2x)CO2

(1)

4+

where x is the Mn ion concentration in Ba2LaSb(1-x)O6:xMn4+ phosphors. The chemicals (BaCO3 (99.9%), La2O3 (99.99%), Sb2O5 (99.99%), and MnCO3 (99.9%)) without further purified are directly used as raw materials. At first, we calculate the weight of the raw materials and accurately weight them according to the composition ratio in Ba2LaSb(1-x)O6:xMn4+ phosphors, put them into an agate morta, and carefully grind them for 20 min to form an uniform mixture. Second, the mixtures are put into an aluminum oxide crucible (5 ml) and heated at 700 °C for 5 h under air condition in high temperature furnace. Thirdly, the mixtures are cooled to room temperature and carefully reground for 15 min. Finally, we calcine the mixtures at 1400 °C for 5 h under air condition again. The properties of samples are measured after they are cooled to room temperature. 2.2. Characterization We use X-ray powder diffractions (XRPD) diffractometer (Philips Model PW1830) with a graphite monochromator using Cu-Kα radiation to confirm the phase formation and crystal structure of the samples. The operated voltage and current are 40 kV and 40 mA, respectively. We collect the XRD patterns data in the 2θ range of 20–90° at room temperature. We measure the morphology of the phosphors by the fieldemission scanning electron microscopy system (FE-SEM, MAIA3 TESCAN) equipped with an energy dispersive X-ray (EDX) spectrum. The operated voltage is 15 V. We investigate luminescence properties, decay curves, temperaturedependence emission spectra as well as time-resolved emission spectra of the phosphors by a steady-state FLS980 spectrofluorimeter (Edinburgh Instruments, UK, Edinburgh) with a high spectral resolution (signal to noise ratio > 12000:1). A 450 W ozone free xenon lamp is used as the excitation source for steady-state spectrum measurement. A microsecond pulsed xenon flash lamp μF900 with an average power of

Fig. 2. XRD patterns of JCPDS no. 54-958 (Ba2LaSbO6) and Ba2LaSb(14+ (x = 0.0, 0.2, 0.6, and 1.0 mol%) phosphors. x)O6:xMn 2

Journal of Luminescence 209 (2019) 1–7

Y. Ren et al.

Fig. 3. EDX spectrum, elemental mapping, atomic percentage, and SEM diagram of Ba2LaSbO6:1%Mn4+ phosphor.

after a small number of Mn4+ ions are doped into the host (Ba2LaSbO6) lattice. Fig. 3 shows EDX spectrum, elemental mapping, atomic percentage, and FE-SEM diagram of Ba2LaSbO6:1%Mn4+ phosphor. It can be well seen that EDX spectrum of Ba2LaSbO6:1%Mn4+ phosphor contains the peaks of Ba, La, Sb, Mn, and O. The peaks derived from Mn4+ ion are very weak because Mn4+ ion content is very few. Combined with the XRD pattern data in Fig. 2, we can affirm that the Ba2LaSbO6:Mn4+ phosphor is successfully synthesized. According to the FE-SEM diagram, it can be found that Ba2LaSbO6:1%Mn4+ phosphor is composed of many irregular sintered microparticles, whose size is in the range of 0.5–2 µm. From the element mapping, it can be confirmed that the Ba, La, Sb, Mn, and O elements are similarly dispersed in the whole particle. Photoluminescence excitation (PLE) spectra of Ba2LaSbO6:0.2% Mn4+ phosphor at room temperature (λem= 654 and 678 nm) are presented in Fig. 4. Monitored at 654 and 678 nm, PLE spectral shape and peak positions of Ba2LaSbO6:0.2%Mn4+ phosphor are the same except the PLE intensity. PLE spectrum of Ba2LaSbO6:0.2%Mn4+ phosphor covers the region from 250 to 575 nm, which contains two broad PLE bands. PLE peaks at ~325, 380, 395, and 508 nm are attributed to the O2- - Mn4+ charge transfer band (CTB), the 4A2 → 4T1, 4 A2 → 2T2, and 4A2 → 4T2 transitions of Mn4+ ion, respectively [26,27]. The PLE spectrum indicates that Ba2LaSbO6:Mn4+ phosphor can be Fig. 5. (a) PL spectra of Ba2LaSbO6:0.2%Mn4+ phosphor at room temperature (λex = 325, 380, and 508 nm) and (b) The absorption spectra of plant photosynthesis [29,30].

effectively excited by the light in the range of 300–450 nm and 470–550 nm. PL spectra of Ba2LaSbO6:0.2%Mn4+ phosphor at room temperature (λex = 325, 380, and 508 nm) are displayed in Fig. 5(a). With excitation at 325, 380, and 508 nm, PL spectral shape and peak positions of Ba2LaSbO6:0.2%Mn4+ phosphor are the same except the PL intensity. PL band in the range of 625–740 nm is assigned to the 2E → 4A2 transition of Mn4+ ion and PL peaks (e.g., 654 and 678 nm) are due to the vibronics of zero-phonon line [28]. In order to study the luminous efficiency, we measure directly the QE by the steady-state FLS980

Fig. 4. PLE spectra of Ba2LaSbO6:0.2%Mn4+ phosphor at room temperature (λem = 654 and 678 nm). 3

Journal of Luminescence 209 (2019) 1–7

Y. Ren et al.

Fig. 6. Tanabe-Sugano energy level diagram of Mn4+ ion in octahedral environment.

spectrofluorimeter with an integrating sphere. When the monitored wavelength is 678 nm with excitation at 380 nm, the QE value of Ba2LaSbO6:0.2%Mn4+ phosphor is about 33.5%. This is said that we must further research and improve the luminous efficiency of Ba2LaSbO6:Mn4+ phosphor for it's practical application in LEDs. Fig. 5(b) shows the absorption spectra of plant photosynthesis, which refer from Refs. [29,30]. It can be well seen that PL spectrum of Ba2LaSbO6:0.2%Mn4+ phosphor with excitation at 325, 380, and 508 nm well matchs with the absorption spectra of plant photosynthesis in the range of 625–740 nm. Combined with the PLE spectra in Fig. 4, it can be confirmed that Ba2LaSbO6:Mn4+ may be used as a deep-redemitting phosphor in red light LEDs and has a good potential application prospect in inroom plant culture. The Tanabe-Sugano energy level diagram of Mn4+ ion in octahedral environment is presented in Fig. 6, which is usually used to explain the luminous mechanism of Mn4+ ion. The free electrons of Mn4+ ion in the ground state (4A2) are transferred to the excited states (4T1, 2T2, and 4 T2) after they absorb the light energy. The free electrons in higher excited states seek to come back to the lower excited states and locate at the excited state (2E) by nonradiative, and finally transfer to the ground state (4A2) by the 2E → 4A2 radiative transition. So, the energy is released as photons, resulting in emission. In Ba2LaSbO6:Mn4+ phosphor, according to the PLE and PL spectral properties, the crystal field strength (Dq), the Racah parameters (B and C), and Dq/B value can be calculated by the following formulas (2–5) [31,32]:

Dq =

E (4 A2 10

Fig. 7. (a) PLE and (b) PL spectra of Ba2LaSb(1-x)O6:xMn4+ (x = 0.1, 0.2, 0.4%, 0.6, 0.8, and 1.0 mol%) phosphors at room temperature. The monitored wavelength is 678 nm and the excitation wavelength is 380 nm. The inset: The relation between PL intensity and Mn4+ content.

the influence of Mn4+ concentration to PL intensity. The monitored wavelength is 678 nm and the excitation wavelength is 380 nm. PLE and PL spectral shapes and peak positions of Ba2LaSbO6:Mn4+ phosphor are the same with increasing Mn4+ concentration. Spectral intensity increases with increasing Mn4+ content when x ≤ 0.002 because of the increase of energy transfer (ET) among adjacent Mn4+ ions. Maximum intensity of the PL and PLE bands is observed when x = 0.002. When x > 0.002, spectral intensity decreases with further increasing Mn4+ content due to the concentration quenching (CQ) of Mn4+ ion. So, we confirm that the optimal Mn4+ ion concentration in Ba2LaSbO6:Mn4+ phosphor is ~0.002. The critical distance (Rc) between adjacent Mn4+ ions presents a significant impact on CQ, which may be calculated by the following formula [33]:

4

T 2)

Rc = 2

(2)

Parameter B can be calculated by the following equation:

Dq 15(x –8) = 2 B x –10x

E (4 A2

(3)

4

E (4 A2

T1)

4

T2) (4)

Dq Parameter C can be calculated by the following equation:

2

4

E( E B

A2 )

=

3.05C + 7.9 B

1.8B Dq

1/3

(6)

where V is the volume of the unit cell, x is the critical doped concentration of Mn4+ ion, and N is the number of sites available for the dopant in the unit cell. V and N can be obtained via the crystal structure of Ba2LaSbO6, here, V = 160.17 Å3 and N = 1. According to the PL spectra in Fig. 7(b), x is 0.002. Thus, Rc value could be calculated to be 53.4 Å, which is much larger than 5 Å. Exchange interaction is the major mechanism for CQ when Rc is less than 5 Å. So, the electric multipolar interaction is the main mechanism of CQ. According to Dexter [34], the type of interaction mechanism can be determined by the following equation:

And x is calculated by the following equation:

x=

3V 4 xN

(5)

log

According to the PLE and PL spectra in Figs. 4 and 5, The peak energies of 4A2 → 4T1 (380 nm), 4A2 → 4T2 (508 nm), and 2E → 4A2 (678 nm) of Mn4+ ion are ~ 26,316, 19,685, and 14,749 cm−1, respectively. On the basis of the Eqs. (2)–(5), the calculation results of Dq, B, C, and Dq/B values are ~ 1969 cm−1, 633 cm−1, 3504 cm−1, and 3.11, respectively. Fig. 7 shows PLE and PL spectra of Ba2LaSb(1-x)O6:xMn4+ (x = 0.1, 0.2, 0.4%, 0.6, 0.8, and 1.0 mol%) phosphors at room temperature and

I = A– log x x 3

(7)

where I is the luminescence intensity, x is the dopant concentration, A is concentration and θ is an index of the electric multipolar character with θ = 6, 8 and 10 corresponds to electric dipole-dipole (d - d), dipolequadrupole (d - q), and quadrupole-quadrupole (q - q) interaction, respectively. The calculation data of lg(I/x) and lg(x) are shown in Fig. 8. So, the slope (-θ/3) can be calculated and is ~ −1.86. The θ value is ~5.58, which is close to 6, indicating that the d-d interaction is the 4

Journal of Luminescence 209 (2019) 1–7

Y. Ren et al.

Fig. 8. The calculation data of lg(I/x) and lg(x).

Fig. 10. Temperature-dependent emission spectra of Ba2LaSb0.998 O6:0.002Mn4+ phosphor in the range of 300–510 K (λex = 380 nm). The inset: The relationship between temperature and PL intensity; (b) The configuration coordinate of Mn4+ ion.

and the decay time interval is 80 μs. It can be well seen that PL intensity decreases and other spectral features remain similar with increasing decay time from 0.08 ms to 4 ms. The decay curves and time-resolved emission spectra combined with the luminescence properties of Ba2LaSbO6:Mn4+ phosphor suggest that there is only a luminescence center (Mn4+) in Ba2LaSbO6:Mn4+ phosphor. The temperature-dependent emission spectra of Ba2LaSb0.998O6:0.002Mn4+ phosphor in the range of 300–510 K is shown in Fig. 10(a). It can be obviously observed that with the increasing temperature from 300 K to 510 K, PL spectra exhibit the same spectral shape and peak positions, but PL intensity becomes weakened gradually because of the thermal quenching (TQ), which is assigned to nonradiative transition in Mn4+. As shown in Fig. 10(b), the normal route of electron transition is to follow the black arrow. Free electrons in Mn4+ ion are raised to excited states (4T1, 2T2, and 4T2) from the ground state (4A2) when they are excited by UV light. The 2E → 4A2 transition can be occurred, photons are released, which produce deepred emission. Once the temperature goes up, the route of electron transition will be changed due to the thermal energy effect. Part of free electrons at the excited state (2E) can come back to the ground state (4A2) along the path of the green arrows via nonradiative transition, decreasing the release of photon. So, the emission intensity decreases. In order to further explore the TQ characteristics, the activation energy (Ea) is studied by the Arrhenius formula [35]:

Fig. 9. (a) Decay curves of Ba2LaSb(1-x)O6:xMn4+ (x = 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) phosphors at room temperature (λem = 678 nm and λex = 380 nm). The red lines are a fit of the experimental data to the first order exponential decay equation; (b) Time-resolved emission spectra of Ba2LaSb0.998O6:0.002Mn4+ phosphor at room temperature (λem = 678 nm and λex = 380 nm). Decay time is in the range of 0.08–4 ms and decay time interval is 80 μs.

main type of interaction mechanism in Ba2LaSbO6:Mn4+ phosphor. The decay curves of Ba2LaSb(1-x)O6:xMn4+ (x = 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) phosphors at room temperature are displayed in Fig. 9(a). The monitored wavelength is 678 nm with excitation at 380 nm. All decay curves are fitted by the first order exponential decay function [32]:

I(t ) = I(0) exp

t

(8)

I=

where I(t) is the luminescence intensity at time t, I(0) is the initial luminescence intensity, t is the time, and τ is the decay time for the exponential components. The lifetimes are determined to be 281.1, 277.1, 250.4, 236.5, 224.4, and 198.2 μs for x = 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%, respectively. Obviously, the lifetime decreases in turn from 281.1 μs to 198.2 μs with increasing Mn4+ concentration from 0.1 mol % to 1.0 mol%. Fig. 9(b) shows the time-resolved emission spectra of Ba2LaSb0.998O6:0.002Mn4+ phosphor at room temperature (λem = 678 nm and λex = 380 nm). Decay time is in the range of 0.08–4 ms

I0 1 + Ae ( Ea / KT )

(9)

The formula 9 may be written as:

In

I0 E –1 = InA– a I KT

(10)

where I0 is the intensity at the initial temperature, I is the intensity at the different temperatures, A is a constant, Ea is the activation energy, and K is the Boltzmann constant. At 300 K, KT = 0.025852 eV. According to PL intensity in Fig. 10(a), the relationship between ln(I0/I-1) 5

Journal of Luminescence 209 (2019) 1–7

Y. Ren et al.

the optimal Mn4+ concent is ~ 0.2 mol%. Luminescence properties, ducay curves, and time-resolved emission spectra confirm that there is only luminescence center (Mn4+) in Ba2LaSbO6:Mn4+ phosphor. Analysis of the temperature-dependence emission spectra of Ba2LaSbO6:Mn4+ phosphor indicates the favorable thermal stability. The luminescence properties indicate that Ba2LaSbO6:Mn4+ phosphor will be used as promising red-emitting phosphor candidates for plantcultivation LEDs. At the same time, the experimental results are helpful to explore the potential rare-earth-free Mn4+ doped red-emitting phosphors. Acknowledgments Fig. 11. The relationship of 1/KT and ln[(I0/I)− 1].

This work is financially supported by the National Natural Science Foundation of China (Nos. 51862015 and 11464021), Foundation of Jiang’xi Educational Committee (No. GJJ180564), and National Undergraduate Training Program for Innovation and Entrepreneurship of China (No. 201810419019). References [1] A. Agarwal, S.D. Gupta, Impact of light-emitting diodes (LEDs) and its potential on plant growth and development in controlled-environment plant production system, Curr. Biotechnol. 5 (2016) 28–43. [2] Z. Zhou, J. Zheng, R. Shi, N. Zhang, J. Chen, R. Zhang, H. Suo, E.M. Goldys, C. Guo, Ab initio site occupancy and far-red emission of Mn4+ in cubic-phase La(MgTi)1/ 2O3 for plant cultivation, ACS Appl. Mater. Interfaces 9 (7) (2017) 6177–6185. [3] R. Cao, Z. Shi, G. Quan, T. Chen, S. Guo, Z. Hu, P. Liu, Preparation and luminescence properties of Li2MgZrO4:Mn4+ red phosphor for plant growth, J. Lumin. 188 (2017) 577–581. [4] J. Liang, L. Sun, B. Devakumar, S. Wang, Q. Sun, H. Guo, B. Li, X. Huang, Novel Mn4+-activated LiLaMgWO6 far-red emitting phosphors: high photoluminescence efficiency, good thermal stability, and potential applications in plant cultivation LEDs, RSC Adv. 8 (2018) 27144–27151. [5] R.M. Metallo, D.A. Kopsell, C.E. Sams, N.R. Bumgarner, Influence of blue/red vs. white LED light treatments on biomass, shoot morphology, and quality parameters of hydroponically grown kale, Sci. Hortic. 235 (2018) 189–197. [6] J. Xiang, J. Chen, N. Zhang, H. Yao, C. Guo, Far red and near infrared doublewavelength emitting phosphor Gd2ZnTiO6:Mn4+, Yb3+ for plant cultivation LEDs, Dye Pigments 154 (2018) 257–262. [7] R. Cao, W. Wang, J. Zhang, S. Jiang, Z. Chen, W. Li, X. Yu, Synthesis and luminescence properties of Li2SnO3:Mn4+ red-emitting phosphor for solid-state lighting, J. Alloy. Compd. 704 (2017), pp. 124–130. [8] Q. Zhou, L. Dolgov, A.M. Srivastava, L. Zhou, Z. Wang, J. Shi, M.D. Dramic′anin, M.G. Brike, M. Wu, Mn2+ and Mn4+ red phosphors: synthesis, luminescence and applications in WLEDs. A review, J. Mater. Chem. C 6 (2018) 2652–2671. [9] L. Xi, Y. Pan, X. Chen, S. Huang, M. Wu, Optimized photoluminescence of red phosphor Na2SnF6:Mn4+ as red phosphor in the application in “warm” white LEDs, J. Am. Ceram. Soc. 100 (5) (2017) 2005–2015. [10] Z. Lu, A. Fu, F. Gao, X. Zhang, L. Zhou, Synthesis and luminescence properties of double perovskite Ba2MgGe2O7:Mn4+ deep red phosphor, J. Lumin. 203 (2018) 420–426. [11] J. Chen, C. Guo, Z. Yang, T. Li, J. Zhao, Li2SrSiO4:Ce3+, Pr3+ phosphor with blue, red, and near-infrared emissions used for plant growth LED, J. Am. Ceram. Soc. 99 (2016) 218–225. [12] Z. Lu, T. Huang, R. Deng, H. Wang, L. Wen, M. Huang, L. Zhou, C. Yao, Double perovskite Ca2GdNbO6:Mn4+ deep red phosphor: potential application for warm WLEDs, Superlattice Microstruct. 117 (2018) 476–487. [13] R. Cao, X. Liu, K. Bai, T. Chen, S. Guo, Z. Hu, F. Xiao, Z. Luo, Photoluminescence properties of red-emitting Li2ZnSn2O6:Mn4+ phosphor for solid-state lighting, J. Lumin. 197 (2018) 169–174. [14] W. Chen, Y. Cheng, L. Shen, C. Shen, X. Liang, W. Xiang, Red-emitting Sr2MgGe2O7:Mn4+ phosphors: structure, luminescence properties, and application in warm white light emitting diodes, J. Alloy. Compd. 762 (2018) 688–696. [15] A.M. Srivastava, M.G. Brik, H.A. Comanzo, W.W. Beers, W.E. Cohen, T. Pocock, Spectroscopy of Mn4+ in double perovskites, La2LiSbO6 and La2MgTiO6: deep red photon generators for agriculture LEDs, ECS J. Solid State Sci. 7 (1) (2018) R3158–R3162. [16] R. Cao, X. ceng, J. Huang, X. Xia, S. Guo, J. Fu, A double-perovskite Sr2ZnWO6:Mn4+ deep red phosphor: synthesis and luminescence properties, Ceram. Int. 42 (15) (2016) 16817–16821. [17] Y. Takeda, H. Kato, M. Kobayashi, S. Nozawa, H. Kobayashi, M. Kakihana, Photoluminescence properties of double perovskite tantalates activated with Mn4+, AE2LaTaO6:Mn4+ (AE = Ca, Sr, and Ba), J. Phys. Chem. C 121 (34) (2017) 18837–18844. [18] R. Cao, J. Zhang, W. Wang, Z. Hu, T. Chen, Y. Ye, X. Yu, Preparation and photoluminescence characteristics of Li2Mg3SnO6:Mn4+ deep red phosphor, Mater. Res. Bull. 87 (2017) 109–113. [19] X. Zhang, J. Nie, S. Liu, Y. Li, J. Qiu, Deep-red photoluminescence and long

Fig. 12. The CIE chromaticity diagram and chromaticity coordinate. The inset: [MnO6] octahedron and the picture under 365 nm UV lamp.

and 1/KT is plotted in Fig. 11. The experimental data can be linear fitted with a slope of −0.405. Thus, the value of Ea for TQ is ~ 0.405 eV, which is bigger than that of NaMgGdTeO6:0.01Mn4+ phosphor (0.2532 eV) [20] and similar to that of Ca2GdNbO6:0.01Mn4+ phosphor (0.412 eV) [12]. We present the Commission International de I′Eclairage (CIE) chromaticity diagram, chromaticity coordinate on the basis of the recorded PL spectrum of Ba2LaSb0.998O6:0.002Mn4+ phosphor, [MnO6] octahedron, and the picture under 365 nm UV lamp in Fig. 12. With excitation at 380 nm, Ba2LaSb0.998O6:0.002Mn4+ phosphor emits deepred light, and the CIE chromaticity coordinates are determined to be about (0.7253, 0.2747), which locate in the deep red region. From the inset, the bright red emission from Ba2LaSb0.998O6:0.002Mn4+ phosphor can be clearly seen with the naked eye under 365 nm UV light. The result indicates that Ba2LaSbO6:Mn4+ phosphor may be promising candidate as deep-red-emitting phosphor for plant-cultivation LEDs. 4. Conclusions In summary, Ba2LaSbO6:Mn4+ phosphor for plant-cultivation LEDs are successfully synthesized in air by the high-temperature solid-state reaction method. Mn4+ ion replaces the Sb5+ ion site in Ba2LaSbO6 host lattice and shows deep-red emission. The excitation spectrum in the range of 250–575 nm is observed, which contains two broad PLE bands. The emission spectrum with PL band peaking at 678 nm in the range of 625–740 nm is observed, which well matches with the requirement of red emission for phototropism. In Ba2LaSbO6:Mn4+ phosphor, the d-d interaction is the main interaction mechanism and 6

Journal of Luminescence 209 (2019) 1–7

Y. Ren et al.

[20] [21] [22] [23] [24] [25] [26]

persistent luminescence in double perovstkite-type La2MgGeO6:Mn4+, J. Am. Ceram. Soc. 101 (2018) 1576–1584. K. Li, H. Lian, R.V. Deun, Site occupancy and photoluminescence properties of a novel deep-redemitting phosphor NaMgGdTeO6:Mn4+ with perovskite structure for w-LEDs, J. Lumin. 198 (2018) 155–162. X. Huang, J. Liang, B. Li, L. Sun, J. Lin, High-efficiency and thermally stable far-redemitting NaLaMgWO6:Mn4+ phosphors for indoor plant growth light-emitting diodes, Opt. Lett. 43 (2018) 3305–3308. P. Cai, L. Qin, C. Chen, J. Wang, S. Bi, S. Kim, Y. Huang, H.J. Seo, Optical thermometry based on vibration sidebands in Y2MgTiO6:Mn4+ double perovskite, Inorg. Chem. 57 (6) (2018) 3073–3081. R. Jose, J. Konopka, X. Yang, A. Konopka, M. Ishikawa, J. Koshy, Crystal structure and dielectric properties of a new complex perovskite oxide Ba2LaSbO6, Appl. Phys. A 79 (2004) 2041–2047. W.T. Fu, D.J.W. Ijdo, X-ray and neutron powder diffraction study of the double perovskites Ba2LnSbO6 (Ln = La, Pr, Nd and Sm), J. Solid State Chem. 178 (2005) 2363–2367. R.D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta Crystallogr. A 32 (1976) 751–767. Q. Peng, R. Cao, Y. Ye, S. Guo, Z. Hu, T. Chen, G. Zheng, Photoluminescence properties of broadband deep-red-emitting Na2MgAl10O17:Mn4+ phosphor, J. Alloy. Compd. 725 (2017) 139–144.

[27] L. Qin, S. Bi, P. Cai, C. Chen, J. Wang, S. Il Kim, Y. Huang, H.J. Seo, Preparation, characterization and luminescent properties of red-emitting phosphor: lila2NbO6 doped with Mn4+ ions, J. Alloy. Compd. 755 (2018) 61–66. [28] K. Li, H. Lian, R.V. Deun, A novel deep red-emitting phosphor KMgLaTeO6:Mn4+ with high thermal stability and quantum yield for w-LEDs: structure, site occupancy and photoluminescence properties, Dalton Trans. 47 (2018) 2501–2505. [29] R. Moore, W.D. Clark, R.S. Kingsley, D. Vodopich, Botany. Wm. C. Brown: New York, 1995. [30] G. Karp, Cell and Molecular Biology, 5th ed, John Wiley & Sons, New Jersey, 2008. [31] Q. Sun, S. Wang, B. Li, H. Guo, X. Huang, Synthesis and photoluminescence properties of deep red-emitting CaGdAlO4:Mn4+ phosphors for plant growth LEDs, J. Lumin. 203 (2018) 371–375. [32] G. Blasse, B.C. Grabmaier, Luminescent Materials, Springer-Verlag, BerlinHeidelberg, 1994. [33] G. Liu, B. Jacquier, Spectroscopic Properties of Rare Earths in Optical Materials, Springer, Berlin, 2005. [34] Q. Huang, W. Ye, G. Hu, X. Jiao, X. Liu, Deep red emission enhancement in Mg28Ge10O48:Mn4+ phosphor by Zn substitution, J. Lumin. 194 (2018) 557–564. [35] S.P. Singh, M. Kim, W.B. Park, J.W. Lee, K.S. Sohn, Discovery of a red-emitting Li3RbGe8O18:Mn4+ phosphor in the alkali-germanate system: structural determination and electronic calculations, Inorg. Chem. 55 (20) (2016) 10310–10319.

7