Synthesis and processing of transparent polycrystalline doped yttrium aluminum garnet: a review

Figures & data

Figure 1. Schematic of light scattering while traveling through isotropic polycrystalline ceramic. Adapted from Tsabit et al. [13].

Table 1. Selection of thermal, optical, physical, and mechanical properties of YAG. Adapted from Kochawattana [14].

Optical Properties
Refractive Index	1.8169 at 1064 nm
Primary Diode Pump Band	808.6 nm
Fluorescence Lifetime	230 µs at 1.0% Nd
Thermal Properties
Thermal Conductivity (20°C)	0.129 W/cm-K
Thermal Diffusivity (20°C)	0.046 cm^2/s
Specific Heat	0.59 J/g-K
Liner Expansion Coefficient	8.2 × 10^−6 /K <100>
	7.7 × 10^−6 /K <110>
	7.8 × 10^−6 /K <111>
Nonlinear Refractive Index	6.13 × 10–20 m^2/W at 1030 nm
Dissipative Fracture Limit	175–200 W/cm
Index Thermal Dependence (dn/dt)	8.9 × 10^−6 K^−1
Physical Properties
Molecular Weight	595.3 g/mole
Crystal Structure	Cubic/garnet
Lattice Constant	1.201 nm
Melting Point	1950°C
Density	4.55 g/cm^3
Knoop Hardness	1350 ± 35 kg/mm^2
Mechanical Properties
Young’s Modulus	282 GPa
Tensile Strength	280 MPa
Poisson’s Ratio	0.28

Figure 2. Phase diagram for Y–Al–O system, adapted from [17].

Figure 3. Unit cell of YAG, adapted from [19,20].

Figure 4. XRD reference patterns of YAG, YAP, YAM, B₂O₃, SiO₂, Y₂O₃, and Al₂O₃.

Figure 5. Fabrication rout map for co-precipitation and SSR methods.

Table 2. Summary of powder synthesis and conventional sintering parameters of YAG-based polycrystalline ceramics.

Material	Powder	Dopant (at. %)	Sintering Aid	Sintering Aid (wt. %)	Dwell Temperature (°C)	Dwell Time (h)	Transparency (%) at 1064 nm	Grain Size Avg. (µm)	Furnace Type	Reference
YAG	SSR^a	0	CaO, MgO	0.5, 0.13	1840	8	84.6	5.3	Tungsten vacuum	[23]
YAG	SSR	0	MgO	0.03	1750	10	79	10	Tungsten vacuum	[24]
YAG	SSR	0	CaO, MgO	0.54, 0.13	1840	8	84.5	5	Tungsten vacuum	[25]
YAG	SSR	0	SiO2	0.14	1750	10	82.9	10.0–25.0	Tungsten vacuum	[26]
YAG	SSR	0	SiO2	0.14	1710	12	68	7	Tungsten vacuum	[27]
YAG	CP^b	0	SiO2	0.14	1700	10	>70	0.5–3	Tungsten vacuum	[28]
YAG	CP	0	–	–	1800	18	83.56	4.8	Tungsten vacuum	[29]
Nd:YAG	SSR	1.1	SiO2	0.14	1750	20	∼80	50	Tungsten vacuum	[6]
Nd:YAG	SSR	1	SiO2, MgO	0.145, 0.1	1780	NR^c	82	10	Tungsten vacuum	[30]
Nd:YAG	SSR	1	SiO2, MgO	0.112, 0.08	1750	20	80.85	5	Tungsten vacuum	[31]
Nd:YAG	SSR	2	SiO2	0.3	1700	5	NR	5.20	Tungsten vacuum	[32]
Nd:YAG	SSR	1	SiO2	0.14	1720	30	82.45	15	Tungsten vacuum	[33]
Nd:YAG	SSR	1.1	SiO2	0.14	1750	20	85	20	Tungsten vacuum	[34]
Nd:YAG	SSR	1	–	–	1760	20	83.28	11.8	Tungsten vacuum	[35]
Nd:YAG	CP	1	–	–	1750	7	80	5	Tungsten vacuum	[15]
Nd:YAG	CP	1	SiO2	0.28	1600	8	82	18	Tungsten vacuum	[36]
Nd:YAG	CP	1	SiO2	NR	1750	20	>80	10	Tungsten vacuum	[37]
Nd:YAG	CP	0.4	–	–	1700	20	NR	2	Tungsten vacuum	[38]
Nd:YAG	CP	0.6	–	–	1750	20	NR	10	Tungsten vacuum	[39]
U:YAG	SSR	0.2	CaO	NR	1900	10	∼80	0.5–8	Tungsten vacuum	[5]
Cr:YAG	SSR	0.1	SiO2, CaO	0.14, 1.59	1750	10	81	0.9	Tungsten vacuum	[40]
YAG	SSR	0	SiO2, MgO	0.11, 0.08	1750	20	∼70	NR	Graphite vacuum	[41]
Nd:YAG	CP	2	SiO2	0.14	1780	10	83.8	10.17	Graphite vacuum	[42]
Nd:YAG	CP	2	SiO2	0.14	1780	10	81	NR	Graphite vacuum	[43]
Nd:YAG	CP	2	SiO2	0.14	1780	20	83.6	10	Graphite vacuum	[44]
Nd:YAG	CP	2	SiO2	0.14	1780	20	81.5	10	Graphite vacuum	[45]
U:YAG	CP	0.5	CaO	0.65	1800	15	NR	3.5	Graphite vacuum	[4]
Nd:YAG	SSR	1	SiO2, B2O3	0.14, 0.07	1600	20	84	0.25–0.4	Ceramic tube with oxygen	[22]
Nd:YAG	SSR	NR	SiO2	0.14	1710	4	> 80	4.95	Ceramic tube with oxygen	[46]

^a SSR = Solid state reaction; ^bCP = Co-precipitation; ^cNR = Not reported.

Figure 6. Schematic of particle packing prior to sintering (a) and after partial sintering which has resulted in a reduced pore size (b). X is the distance between the center of the particles, this distance is reduced as sintering occurs. Replotted from L. F. Francis [48].

Figure 7. Change in transmittance of Yb:YAG sintered at 1750°C for 15 h as a result of ball milling time (black solid: approximate particle size; red circle: 600-nm wavelength; blue triangle: 1100-nm wavelength). Plotted based on datasets from Chen et al. [57].

Figure 8. Effect of powder crystallinity on transmittance of Nd:YAG samples sintered at 1780°C for 10 h. S1–S3: calcination at 1100°C for 2, 4, 6 h, respectively. S4–S6: calcination at 1150, 1200, 1250°C respectively for 4 h. The sample S6 has the highest degree of crystallinity. Reprinted with permission from Ma et al. [43].

Figure 9. XRD results of powders calcinated at various temperatures. Reprinted with permission from Sang et al. [28].

Figure 10. SEM images of grain structure of sintered samples calcinated at different temperatures: (a) 900°C, (b) 1000°C, (c) 1100°C, (d) 1200°C, (e) 1300°C, (f) in-line transmittance plot of the sample shown in (e). Reprinted with permission Sang et al. [28].

Figure 11. Illustration of packing structures within a green body ceramic as a result of powder morphology. Reprinted with permission from Uematsu [59].

Figure 12. Schematic of consolidation methods for producing ceramic green bodies. Replotted from Crouch et al. [60].

Figure 13. In-line transmission plot of polycrystalline 1 at. % Nd:YAG samples with the same sintering aids of SiO₂ and B₂O₃ in flowing O₂ compared to vacuum atmosphere. Reprinted with permission from Stevenson et al. [22].

Figure 14. Relative density of polycrystalline YAG sintered in vacuum vs. air at given temperatures. Reprinted with permission from Mohammadi et al. [27].

Figure 15. Grain size increases with the increase of SiO₂ concentration at given temperatures. Reprinted with permission from Stevenson [81].

Figure 16. SEM images of mirror polished (top) and fractured (bottom) polycrystalline YAG with sintering aids of (A) 0.14 wt. % SiO₂, (B) 0.145 wt. % SiO₂ + 0.10 wt. % MgO, and (C) 0.10 wt. % MgO. Reprinted with permission from Yang et al. [30].

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