Synthesis, Luminescent Properties and White LED Fabrication of Sm3+ Doped Lu2WMoO9
Round 1
Reviewer 1 Report
The manuscript deals with the optical properties of Sm doped Lu2(Lo,W)2O9 materials with possible applications for white lightening. The paper is well written and pleasant to read. Nevertheless, prior to full acceptance let me ask for extra data.
- If a use of these materials is envisioned as phosphors for UV-LED (as suggested by the authors), please determine the quantum yield and discuss the evolution of emission intensity versus temperature (at least up to 200°C). Without these pieces of information, the authors cannot say at all if the materials are of interest of not for the target application!
- Can the authors compare the measured CIEx,y parameters to those expected for white lightening?
- Can the authors discuss the nature of the energy transfer mechanism at work in these materials?
- The authors put forwards the high cost of Europium compared to Samarium in the introduction. This point should be discussed a little more. Hence, can they compare the prices per tonne (industry) and per gram (laboratory) for Eu and Sm to convince the readers?
- In section 2, the authors speak about a Lu2O3:Sm2O3 98:2 ratio. In section 3, this ratio is 99:1.
- In section 3.1 (but also line 141), the symbol Eu appears instead of Sm.
- Based on the reading of the section 3.1 and the observation of Figure 1, we don't know if prepared materials are pure. I would expect a Rietveld analysis of each X-ray diffraction pattern.
- In Figure 5, the formula Lu2(W1.5Mo1.5)O4 should be replaced by Lu2(W1.5Mo1.5)O12
Author Response
Dear editor and reviewers:
Thank you very much for your hard work on the manuscript. For there is too much mistakes in the original manuscript, we won’t list the corrections in detail and typed them in blue color in the revised manuscript. I feel sorry for the work may let you feel uncomfortable for the work is not in detail and bad writing. Thank you very much for giving us a chance to revise the manuscript. We hope that the revised manuscript has reached the publishing level. Whatever, thank you very much again.
Reviewer 1# The manuscript deals with the optical properties of Sm doped Lu2(Mo,W)2O9 materials with possible applications for white lightening. The paper is well written and pleasant to read. Nevertheless, prior to full acceptance let me ask for extra data.
1. If a use of these materials is envisioned as phosphors for UV-LED (as suggested by the authors), please determine the quantum yield and discuss the evolution of emission intensity versus temperature (at least up to 200°C). Without these pieces of information, the authors cannot say at all if the materials are of interest of not for the target application!
Answer: Thank you very much for your suggestions. For the present experimental conditions are difficult to measure the quantum yield and the restriction of the revision time, we won’t provide the quantum yield data this time. As you suggested, the temperature dependent PL emission spectra were recorded and added in Figure 8 as inset of (c). At 150 oC, the intensity maintained 67% intensity of 50 oC. Figure 8 was updated and some sentences were added in the revised manuscript: In addition, the temperature dependent emission intensities are measured and added as inset of (c) in Figure. 8. With the temperature increasing from 50 oC to 250 o, the emission intensity decreased continuously. At 150 oC, the emission intensity maintained 67% intensity of 50 oC. The abstract part and the conclusion part were added some sentences, too.
2. Can the authors compare the measured CIEx,y parameters to those expected for white lightening?
Answer: The obtained chromaticity coordinates are (0.453, 0.346), which deviated from the white point (0.333, 0.333). And the measured chromaticity coordinates of LED have great effects on the dosage of the phosphors, we dare not to discuss this in depth for we did not fabricate the LEDs too much. We revised the writing to: the chromaticity coordinates were (0.453, 0.346), which deviated slightly from the white standard point (0.333, 0.333).
3. Can the authors discuss the nature of the energy transfer mechanism at work in these materials?
Answer: Thank you very much for your question. We referred some reference such as [16] Wang, Y.; Deng, B.; Ke, Y.; Shu, S.; Liu, R.X.; Yu, R.J. Spectroscopic investigation of La7Ta3W4O30:Sm3+ orange-red phosphor for white LEDs. Arab. J. Chem. 2020, 13, 5581–5592. 29. [29] Xiong, F.B.; Guo, D.S.; Lin, H.F.; Wang, L.J.; Shen, H.X.; Zhang, W.Z. High-color-purity red-emitting phosphors RE2WO6:Pr3+ (RE = Y, Gd) for blue LED. J. Alloy. Compd. 2015, 647, 1121–1127. [30] Deng, Y.M.; Yi, S.P.; Huang, J.; Xian, J.Q.; Zhao, W.R. White light emission and energy transfer in Dy3+/Eu3+ co-doped BaLa2WO7 phosphors. Mater. Res. Bull. 2014, 57, 85–90. [31] Hou, D.J.; Pan, X.X.; Li, J.Y.; Zhou. W.J.; Ye. X.Y. Structure and luminescence properties of Sm3+ doped Y2MoO6 phosphor under near ultraviolet light excitation. J. Rare Earths 2017, 35, 335–340. We believed that the excitation energy was mainly absorbed by host lattice, then transferred the energy to Sm3+. As you suggested, we should refine the XRD data and can analyze the mechanism concretely. We discussed the energy transfer based on the PL spectra briefly. By monitoring at Sm3+ 614 nm emission, there is a broad CTB absorption from host lattice, we describe that the absorption energy can be transferred to the higher excited states of Sm3+. About the ET mechanism, we should measure some new data (quantum efficiency, lifetime, or intensities) and synthesize new materials (undoped material). For the restriction of the revision time, we have no enough time to do this. We’ll do concrete work in future. Thank you very much for your suggestions.
4. The authors put forwards the high cost of Europium compared to Samarium in the introduction. This point should be discussed a little more. Hence, can they compare the prices per tonne (industry) and per gram (laboratory) for Eu and Sm to convince the readers?
Answer: The original description is subjective and we cannot give the authoritative prices to convince the readers. We revised the sentence “For the high cost of the Eu3+, new red emitter should be explored, too.” to “As an alternative choice of Eu3+, new red emitters need to be explored, too.” We’ll attention this in future.
5. In section 2, the authors speak about a Lu2O3:Sm2O3 98:2 ratio. In section 3, this ratio is 99:1.
Answer: That’s the basic mistake and I feel sorry for that. We designed the experiment with the ratio of 99:1, yet the mass of Sm2O3 is a little difficult to weigh identically for the comparation of the three samples. We changed the ratio to 98:2, yet we confused these in the writing and the design. We confirm that the ratio is 98:2 and revised the writing in section 3.
6. In section 3.1 (but also line 141), the symbol Eu appears instead of Sm.
Answer: I feel embarrassed for this. For we wrote another manuscript about Eu3+ doping, we copied some sentences from that manuscript and didn’t check the writing carefully. I feel sorry for that.
7. Based on the reading of the section 3.1 and the observation of Figure 1, we don't know if prepared materials are pure. I would expect a Rietveld analysis of each X-ray diffraction pattern.
Answer: Thank you very much for your suggestions. We want to practice the Rietveld analysis of the XRD data very much. In fact, we did not know how to analyze the data without the concrete reference data. Some of our members are studying the analysis and we hope that we’ll learn how to deal that in future. Your comments will encourage us to work hard in future. Thank you very much.
8. In Figure 5, the formula Lu2(W1.5Mo1.5)O4 should be replaced by Lu2(W1.5Mo1.5)O12
Answer: I feel sorry for my carelessness. I have revised the writing. For consistency, the writing Lu2(W1.5Mo1.5)O4 was revised to Lu2(Mo0.5W0.5O4)3 in Figure 5. Thank you very much. We’ll work carefully in future.
Reviewer 2 Report
1. Regarding the discussion on current available phosphors in "The present used commercial phosphor based W-LEDs are usually based on the combination of blue LED chips with Y3Al5O12:Ce3+ (YAG:Ce3+) yellow phosphors.", authors should give some representative works such as in https://doi.org/10.1002/lpor.201300140. For the similar material family compared with the LuWMoxOy membrane, authors should also mention the LuAlxOy membrane such as in https://doi.org/10.1016/j.cej.2021.128754 and https://doi.org/10.1109/JLT.2017.2785320. These references should be addressed for a complete overview for comparison. 2. Except the present discussion for Fig. 8, authors can emphasize more on the description of color temperature and color rendering index which have been obtained with their proposed phosphors. Please add these parameters into the related paragraph and also give a comparison table for a fair comparison with other candidates as aforementioned series with similar membrane or chemical composition. These would help research peers understanding the developing progress and the importance of this work as compared to previous contributions. Overall, this is a very intriguing material system with promising applicability for lighting industry in the near future, it can be accepted after minor revision.
Author Response
Dear editor and reviewers:
Thank you very much for your hard work on the manuscript. For there is too much mistakes in the original manuscript, we won’t list the corrections in detail and typed them in blue color in the revised manuscript. I feel sorry for the work may let you feel uncomfortable for the work is not in detail and bad writing. Thank you very much for giving us a chance to revise the manuscript. We hope that the revised manuscript has reached the publishing level. Whatever, thank you very much again.
Reviewer 2# 1. Regarding the discussion on current available phosphors in "The present used commercial phosphor based W-LEDs are usually based on the combination of blue LED chips with Y3Al5O12:Ce3+ (YAG:Ce3+) yellow phosphors.", authors should give some representative works such as in https://doi.org/10.1002/lpor.201300140. For the similar material family compared with the LuWMoxOy membrane, authors should also mention the LuAlxOy membrane such as in https://doi.org/10.1016/j.cej.2021.128754 and https://doi.org/10.1109/JLT.2017.2785320. These references should be addressed for a complete overview for comparison.
Answer: Thank you very much for your providing some excellent papers to us. We asked some friends to download them to us, studied them carefully and added them in the revised manuscript. The works are beautiful and we’ll try our best to keep up with the researchers though it is difficult.
2. Except the present discussion for Fig. 8, authors can emphasize more on the description of color temperature and color rendering index which have been obtained with their proposed phosphors. Please add these parameters into the related paragraph and also give a comparison table for a fair comparison with other candidates as aforementioned series with similar membrane or chemical composition. These would help research peers understanding the developing progress and the importance of this work as compared to previous contributions. Overall, this is a very intriguing material system with promising applicability for lighting industry in the near future, it can be accepted after minor revision.
Answer: Thank you very much for your suggestions. For the properties of the fabricated LEDs greatly depend on the dosage of the phosphors, we dare not to discuss the properties in detail. The presented LED chromaticity coordinates are (0.453, 0.346), the color temperature is 2260 K, the color purity is 0.397, yet the color rendering index is not provided. Another LED which was not illustrated in manuscript, the chromaticity coordinates are (0.374, 0.298), the color temperature is 3354 K, the color purity is -0.125, yet the color rendering indexes are (92.4 89.7 93.3 85.4 90.1 86.8 83.9 85.6 71.5 85.5 89.5 59.2 87.6 96.9) respectively. The data suggest that the fabrication procedure has a lot work to do. The comparison has no meaning. For the time restriction of the revision, we won’t fabricate the LEDs again and will do deep research in future work. We added one sentence in the revised manuscript: The measured color temperature was 2260 K, and the color purity was 0.397. Thank you very much for your suggestions.
Round 2
Reviewer 1 Report
I accept this revised version even if the authors didn't answer to all of my requests.
