REFERENCES

1. Basu B, Vitchev RG, Vleugels J, Celis JP, Van Der Biest O. Influence of humidity on the fretting wear of self-mated tetragonal zirconia ceramics. Acta Mater 2000;48:2461-71.

2. Lv H, Bao J, Qi S, Jin Q, Guo W. Optical and mechanical properties of purple zirconia ceramics. J Asian Ceram 2019;7:306-11.

3. Goeb O, Herrmann M, Siegel S. Thermodynamic and microstructural studies of coloration and decoloration processes during gas-pressure sintering of silicon nitride ceramics. Key Eng Mater 1998;161-3:217-20.

4. Liu N, Zhang J, Duan Y, Li X, Dong S. Effect of rare earth oxides addition on the mechanical properties and coloration of silicon nitride ceramics. J Eur Ceram Soc 2020;40:1132-8.

5. Yada M, Mihara M, Mouri S, Kuroki M, Kijima T. Rare earth (Er, Tm, Yb, Lu) oxide nanotubes templated by dodecylsulfate assemblies. Adv Mater 2002;14:309-13.

6. Wang HQ, Batentschuk M, Osvet A, Pinna L, Brabec CJ. Rare-earth ion doped up-conversion materials for photovoltaic applications. Adv Mater 2011;23:2675-80.

7. Carnall WT, Fields PR, Rajnak K. Spectral intensities of the trivalent lanthanides and actinides in solution. II. Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, and Ho³⁺. J Chem Phys 1968;49:4412-23.

8. Carnall WT, Fields PR, Rajnak K. Electronic energy levels of the trivalent lanthanide aquo ions. IV. Eu³⁺. J Chem Phys 1968;49:4450-5.

9. Ren F, Ishida S, Takeuchi N. Color and vanadium valency in V-doped ZrO₂. J Am Chem Soc 1993;76:1825-31.

10. Newman L, Lafleur WJ, Brousaides FJ, Ross AM. A spectrophotometric investigation of vanadium(V) species in alkaline solutions. J Am Chem Soc 1958;80:4491-5.

11. Ocaña M, González-Elipe AR, Andrés-Vergés M, Tartaj P, Serna CJ, Orera VM. Preparation by hydrolysis of aerosols and colour properties of Cr-doped and Co-doped zircon powders. J Eur Ceram Soc 1998;18:821-30.

12. Haubner R, Herrmann M, Lux B, et al. High performance non-oxide ceramics II. Berlin, Heidelberg: Springer; 2003.

13. Wu DN, Gong XY, Cui RR, Deng CY. Luminescence properties of Ca²⁺ and Si⁴⁺ co-doped strontium molybdate red phosphors for white LEDs. J Mater Sci Mater Electron 2016;27:9661-7.

14. Vinothkumar G, Rengaraj S, Arunkumar P, Cha SW, Suresh Babu K. Ionic radii and concentration dependency of RE³⁺ (Eu³⁺, Nd³⁺, Pr³⁺, and La³⁺)-doped cerium oxide nanoparticles for enhanced multienzyme-mimetic and hydroxyl radical scavenging activity. J Phys Chem C 2019;123:541-53.

15. Cinibulk MK, Thomas G, Johnson SM. Fabrication and secondary-phase crystallization of rare-earth disilicate-silicon nitride ceramics. J Am Ceram Soc 1992;75:2037-43.

16. Wang L, Qi Q, Cai P, et al. New route to improve the fracture toughness and flexural strength of Si₃N₄ ceramics by adding FeSi₂. Scr Mater 2017;126:11-4.

17. Iizuka T, Hyuga H, Kita H, Osumi K. In situ synthesis of Mo₅Si₃ particle reinforced Si₃N₄ composite with crystallized grain boundary phase of Yb₂Si₂O₇. Mater Sci Eng A 2005;395:160-6.

18. Ahmad S, Ludwig T, Herrmann M, Mahmoud M, Lippmann W, Seifert H. Phase evaluation during high temperature long heat treatments in the Y₂O₃-Al₂O₃-SiO₂ system. J Eur Ceram Soc 2014;34:3835-40.

19. Murakami Y, Yamamoto H. Phase equilibria and properties of glasses in the Al₂O₃-Yb₂O₃-SiO₂ system. J Ceram Soc Japan 1993;101:1101-6.

20. Richter HJ, Herrmann M, Hermel W. Calculation of heterogeneous phase equilibria in the system Si-Mg-N-O. J Eur Ceram Soc 1991;7:3-9.

21. Zhang B, Zhuang H, Li W. Phase evolution of Y-α/β-sialon ceramic with YAG as a sintering additive. J Mater Sci Lett 2001;20:101-3.

22. Santos C, Ribeiro S, Strecker K, Suzuki PA, Kycia S, Silva CRM. Crystallographic characterization of silicon nitride ceramics sintered with Y₂O₃-Al₂O₃ or E₂O₃-Al₂O₃ additions. Ceram Int 2009;35:289-93.

23. Hayashi T, Munakata H, Suzuki H, Saito H. Pressureless sintering of Si₃N₄ with Y₂O₃ and Al₂O₃. J Mater Sci 1986;21:3501-8.

24. Zhao DL, Zhang YJ, Gong HY, Nie LF, Zhao L. Effects of sintering aids on mechanical and dielectric properties of Si₃N₄ ceramics. Mater Res Innov 2010;14:338-41.

25. Ikesue A, Furusato I, Kamata K. Fabrication of polycrystal line, transparent YAG ceramics by a solid-state reaction method. J Am Ceram Soc 1995;78:225-8.

26. Ikesue A, Kinoshita T, Kamata K, Yoshida K. Fabrication and optical properties of high-performance polycrystalline Nd:YAG ceramics for solid-state lasers. J Am Ceram Soc 1995;78:1033-40.

27. Tauc J, Grigorovici R, Vancu A. Optical properties and electronic structure of amorphous germanium. Mater Res Bull 1966;15:627-37.

28. Tauc J, Menth A. States in the gap. J Non Cryst Solids 1972;8-10:569-85.

29. Duan Y, Zhang K, Xie X. Electronic structural properties of β-C₃N₄, β-Si₃N₄ and β-Ge₃N₄. Phys Status Solidi B 1997;200:499-508.

30. Yu B, Chen D. First-principles study on the electronic structure and phase transition of α-, β-and γ-Si₃N₄. Acta Phys Sin 2012;61:197102.

31. Nogami M, Abe Y. Fluorescence spectroscopy of silicate glasses codoped with Sm²⁺ and Al³⁺ ions. J Appl Phys 1997;81:6351-6.

32. Krstic Z, Krstic VD. Silicon nitride: the engineering material of the future. J Mater Sci 2012;47:535-52.

33. Kleebe HJ, Pezzotti G, Ziegler G. Microstructure and fracture toughness of Si₃N₄ ceramics: combined roles of grain morphology and secondary phase chemistry. J Am Ceram 1999;82:1857-67.

34. Liang YN, Lee SW, Park DS. Sliding behaviors of a unidirectionally oriented Si₃N₄W/Si₃N₄ composite. Wear 1999;224:202-10.

35. Hardie D, Jack KH. Crystal structures of silicon nitride. Nature 1957;180:332-3.

36. Lee MR, Russell SS, Arden JW, Pillinger CT. Nierite (Si₃N₄), a new mineral from ordinary and enstatite chondrites. Meteoritics 1995;30:387-98.

37. Ponath P, Hamze AK, Posadas AB, et al. Surface structure analysis of Eu Zintl template on Ge(001). Surf Sci 2018;674:94-102.

38. Krishnan R, Swart HC. Cathodoluminescence properties of monoclinic phased reddish-orange emitting BaY₂(MoO₄)₄:Eu³⁺ phosphor. Opt Mater 2020;99:109604.

39. Rakov N, Ramos FE, Hirata G, Xiao M. Strong photoluminescence and cathodoluminescence due to f-f transitions in Eu³⁺ doped Al₂O₃ powders prepared by direct combustion synthesis and thin films deposited by laser ablation. Appl Phys Lett 2003;83:272-4.

40. Qiao J, Xia Z. Design principles for achieving red emission in Eu²⁺/Eu³⁺ doped inorganic solids. J Appl Phys 2021;129:200903.

41. Becher PF. Microstructural design of toughened ceramics. J Am Ceram Soc 1991;74:255-69.

42. Hirosaki N, Okada A, Matoba K. Sintering of Si₃N₄ with the addition of rare-earth oxides. J Am Ceram Soc 1988;71:C-144-7.

43. Mitomo M, Uenosono S. Microstructural development during gas-pressure sintering of α-silicon nitride. J Am Ceram Soc 1992;75:103-7.

44. Kawashima T, Okamoto H, Yamamoto H, Kitamura A. Grain size dependence of the fracture toughness of silicon nitride ceramics. J Ceram Soc Japan 1991;99:320-3.

45. Ding Q, Zhang Y, Chen X, et al. Tuning element distribution, structure and properties by composition in high-entropy alloys. Nature 2019;574:223-7.