Introduction and Objectives: This study aims to enhance the optical properties of polycrystalline alumina by controlling grain growth and minimizing structural defects. To achieve this, the influence of amorphous silicon nitride (Si₃N₄) nanoparticles as a reinforcing agent, in conjunction with MgO and La₂O₃ as sintering aids, on the infrared transmittance of PA was investigated. Furthermore, the role of the dispersing agent in improving slurry homogeneity and particle distribution was evaluated. Materials and Methods: The composite materials were synthesized via a chemical precipitation process, wherein alumina powder was mixed with Si3N4 nanoparticles, magnesium nitrate, lanthanum nitrate, and a dispersing agent in an aqueous solution.Ultrasonic waves were employed to enhance particle dispersion, and the slurry pH was adjusted to 10 to stabilize the suspension.Subsequent to powder preparation, spark plasma sintering was utilized to achieve densification and control grain growth. The microstructural and optical characteristics of the samples were then analyzed using X-ray diffraction, field emission scanning electron microscopy and infrared spectroscopy. Results: The findings indicated that the incorporation of Si3N4 nanoparticles (0.1 wt%) and a dispersing agent (2 wt%) led to an enhancement in infrared transmittance, with a maximum achieved of 85% within the 5–6 µm wavelength range. This observation was corroborated by microscopic analysis, which confirmed a reduction in grain size and an improvement in microstructural uniformity. Furthermore, X-ray diffraction analysis substantiated the preservation of the crystalline structure of alumina across all samples. Conclusion: The optimization of the sintering process, in conjunction with the incorporation of silicon nitride nanoparticles, facilitates the fabrication of transparent alumina, which exhibits augmented optical properties. These materials hold considerable promise for applications in infrared-sensitive systems, including missile guidance and optical sensor technologies.
Jiang D, Hulbert DM, Anselmi‐Tamburini U, Ng T, Land D, Mukherjee AK. Optically transparent polycrystalline Al2O3 produced by spark plasma sintering. J Am Ceram Soc. 2008 ;91(1):151-4. https://doi.org/10.1111/j.1551-2916.2007.02086.x
Gledhill AD, Li D, Mroz T, Goldman LM, Padture NP. Strengthening of transparent spinel/Si3N4 Acta Mater. 2012;60(4):1570-5. https://doi.org/10.1016/j.actamat.2011.11.053
Apetz R, Van Bruggen MP. Transparent alumina: a light-scattering model. J Am Ceram Soc. 2003;86(3):480-6. https://doi.org/10.1111/j.1151-2916.2003.tb03325.x
Krell A, Hutzler T, Klimke J. Transmission physics and consequences for materials selection, manufacturing, and applications. J Eur Ceram Soc. 2009;29(2):207-21. https://doi.org/10.1016/j.jeurceramsoc.2008.03.025
Krell A, Baur GM, Dahne C. Transparent sintered sub-µm Al2O3 with IR transmissivity equal to In: Window and Dome Technol Mater. 2003; 5078:199-207. https://doi.org/10.1117/12.485770
Zhang J, Liu F, Liu P, He D. Transparent alumina nanoceramics prepared under high pressure and low temperature. Adv Eng Mater. 2023;25(5):2101413. https://doi.org/10.1002/adem.202101413
Ratzker B, Wagner A, Kalabukhov S, Frage N. Improved alumina transparency achieved by high-pressure spark plasma sintering of commercial powder. Ceram Int. 2020;46(13):21794-9. https://doi. org/10.1016/j.ceramint.2020.05.198
Boldin MS, Popov AA, Lantsev EA, Nokhrin AV, Chuvil’deev VN. Investigation of the densification behavior of alumina during spark plasma sintering. Materials. 2022;15(6):2167. https://doi.org/10.3390/ ma15062167
Loghman Estarki MR, Abedi Vellashani F, Moinifard F, Milani M, Kumar A, Ghazi MR, Sardarian M. Investigations of selected mechanical, wear properties and transparency of alumina obtained by combined PIM and SPS techniques. J Korean Ceram Soc. 2022;59(6):909-19. https://doi.org/10.1007/s43207-022-00233-w
Milisavljevic I, Pitcher MJ, Li J, Chenu S, Allix M, Wu Y. Crystallization of glass materials into transparent optical ceramics. Int Mater Rev. 2023;68(6):648-76. https://doi.org/10.1080/09506608.2022.2107372
Zhang J, Zhang C, Zhang S, Zhang W. Mechanical properties and toughening mechanism of B4C–Al2O3 composite ceramics prepared by hot-press sintering. Ceram Int. 2024;50(13):24499-507. https://doi.org/ 10.1016/j.ceramint.2024.04.183
Shi Y, He Q, Wang A, Ren Y, Wang J, Wang H, Wang W, Fu Z. Effect of additive content on texture evolution and mechanical properties of Si3N4 ceramics prepared by hot pressing. Mater Sci Eng A. 2024; 898:146348. https://doi.org/10.1016/j.msea.2024.146348
Yin J, Li X, Zhang X, Yu S, Lai Y. Progress in sintering technology of transparent polycrystalline alumina ceramics. J Adv Dielectr. 2024;14(6). https://doi.org/10.1142/S2010135X23300025
An L, Shi R, Mao X, Zhang B, Li J, Zhang J, Wang S. Fabrication of AlON transparent ceramics with Si3N4 sintering additive. J Adv Ceram. 2023;12(7). https://doi.org/10.26599/JAC.2023.9220760
Zhang Z, Liu Y, Liu H. Mechanical properties and microstructure of spark plasma sintered Al2O3-SiCW-Si3N4 composite ceramic tool materials. Ceram Int. 2022;48(4):5527-34. https://doi.org/10. 1016/j.ceramint.2021.11.097
Jiang D, Hulbert DM, Anselmi-Tamburini U, Ng T, Land D, Mukherjee AK. Spark plasma sintering and forming of transparent polycrystalline Al2O3 windows and domes. In: Window and Dome Technol Mater X. 2007; 6545:86-93. https://doi.org/10.1117/ 12.730861
Parish MV, Pascucci MR, Rhodes WH. Aerodynamic IR domes of polycrystalline alumina. In: Window and Dome Technol Mater IX. 2005; 5786:195-205. https://doi.org/10.1117/12.604596
Gao H, Alkaaby HH, Hachim SK, Lafta HA, Zahra MM, Abbas ZS, Kubaisy MM, Rheima AM, Al-Majdi K, Shams MA, Estarki MR. Investigation of mechanical properties and transparency of spark plasma sintered Mg2+ and Y3+ codoped α-Al2O3 nanoparticles synthesized via coprecipitation. J Mater Res Technol. 2023; 23:1052-61. https://doi.org/10. 1016/j.jmrt.2023.01.020
Kim DS, Lee JH, Sung RJ, Kim SW, Kim HS, Park JS. Improvement of translucency in Al2O3 ceramics by two-step sintering technique. J Eur Ceram Soc. 2007; 27(13-15): 3629-32. https://doi.org/10.1016/j. jeurceramsoc.2007.02.002
Chakravarty D, Bysakh S, Muraleedharan K, Rao TN, Sundaresan R. Spark plasma sintering of magnesia-doped alumina with high hardness and fracture toughness. J Am Ceram Soc. 2008;91(1): 203-8. https://doi.org/10.1111/j.1551-2916.2007.02094.x
Xuan S, Tian Y, Kong X, Hao J, Wang X. Effect of different MgO/Al2O3 ratios on microstructural densification, sintering process and mechanical property of MgAl2O4 J Mater Res Technol. 2023; 25: 2518-26. https://doi.org/10.1016/j.jmrt.2023.06.044
Jia XT, Zhang ZH, Xu TH, Liu LJ, Sun YH, Li XY, Wang Q, Jia ZH, He YY, Cheng XW. Effects of sintering aids on microstructure, mechanical, and optical properties of AlON ceramics synthesized by SPS. J Am Ceram Soc. 2023; 106(10):6301-16. https://doi.org/10.1111/jace.19239
Park CW, Yoon DY. Effects of SiO2, CaO2, and MgO additions on the grain growth of alumina. J Am Ceram Soc. 2000; 83(10): 2605-9. https://doi.org/10.1111/j.1151-2916.2000.tb01596.x
Stuer M, Zhao Z, Aschauer U, Bowen P. Transparent polycrystalline alumina using spark plasma sintering: effect of Mg, Y and La doping. J Eur Ceram Soc. 2010; 30(6):1335-43. https://doi.org/10.1016/j.jeurceramsoc.2009.12.001
Aydogmus D, Duygulu O, Sahin FC. In-situ spark plasma sintering behavior of La2O3–Y2O3 co-doped AlON ceramics: An attempt to prevent carbon contamination. J Mater Res Technol. 2023; 27:2323-35. https://doi.org/10.1016/j.jmrt.2023.10.047
He Q, Yang C, Yang L, Xu X. Innovative solid liquid method for lowering the ductile to brittle transition temperature of a La2O3 doped tungsten alloy. SSRN Electron J. 2024. Available at: http://dx.doi.org/ 10.2139/ssrn.4741607
Roussel N, Lallemant L, Chane‐Ching JY, Guillemet‐Fristch S, Durand B, Garnier V, Bonnefont G, Fantozzi G, Bonneau L, Trombert S, Garcia‐Gutierrez D. Highly dense, transparent α‐Al2O3 ceramics from ultrafine nanoparticles via a standard SPS sintering. J Am Ceram Soc. 2013; 96(4):1039-42. https://doi.org/10.1111/jace.12255
Shi X, Zhai W, Wang M, Xu Z, Yao J, Song S, ud Din AQ, Zhang Q. Tribological performance of Ni3Al–15 wt% Ti3SiC2 composites against Al2O3, Si3N4 and WC-6Co from 25 to 800 °C. Wear. 2013;303(1-2):244-54. https://doi.org/10.1016/j.wear.2013.03.034
Darabi, M. , Mohammad Sharifi, E. , Vafaie, R. , Eshaghi, A. and Loghman Estraki, M. R. (2026). Effect of Amorphous Si₃N₄ Nanoparticles on the Infrared Transmittance of α-Al₂O₃. Journal of Advanced Materials in Engineering (Esteghlal), 44(Issue 2 (Serial Number 49)), 79-92. doi: 10.47176/jame.44.2.1102
MLA
Darabi, M. , , Mohammad Sharifi, E. , , Vafaie, R. , , Eshaghi, A. , and Loghman Estraki, M. R. . "Effect of Amorphous Si₃N₄ Nanoparticles on the Infrared Transmittance of α-Al₂O₃", Journal of Advanced Materials in Engineering (Esteghlal), 44, Issue 2 (Serial Number 49), 2026, 79-92. doi: 10.47176/jame.44.2.1102
HARVARD
Darabi, M., Mohammad Sharifi, E., Vafaie, R., Eshaghi, A., Loghman Estraki, M. R. (2026). 'Effect of Amorphous Si₃N₄ Nanoparticles on the Infrared Transmittance of α-Al₂O₃', Journal of Advanced Materials in Engineering (Esteghlal), 44(Issue 2 (Serial Number 49)), pp. 79-92. doi: 10.47176/jame.44.2.1102
CHICAGO
M. Darabi , E. Mohammad Sharifi , R. Vafaie , A. Eshaghi and M. R. Loghman Estraki, "Effect of Amorphous Si₃N₄ Nanoparticles on the Infrared Transmittance of α-Al₂O₃," Journal of Advanced Materials in Engineering (Esteghlal), 44 Issue 2 (Serial Number 49) (2026): 79-92, doi: 10.47176/jame.44.2.1102
VANCOUVER
Darabi, M., Mohammad Sharifi, E., Vafaie, R., Eshaghi, A., Loghman Estraki, M. R. Effect of Amorphous Si₃N₄ Nanoparticles on the Infrared Transmittance of α-Al₂O₃. Journal of Advanced Materials in Engineering (Esteghlal), 2026; 44(Issue 2 (Serial Number 49)): 79-92. doi: 10.47176/jame.44.2.1102