Gadolinium gallium garnet

Gadolinium gallium garnet
General
Category	synthetic mineral
Formula (repeating unit)	Gd3Ga5O12[1]
Crystal system	cubic
Identification
Color	transparent, colorless to light brown or yellow. May also be orange or blue.[1]
Mohs scale hardness	6.5[1] (other sources 7.5)
Luster	vitreous to subadamantine[1]
Specific gravity	7.05 (+.04, -.10)[1]
Density	7.08 g/cm^3
Polish luster	vitreous to subadamantine[1]
Optical properties	Single refractive[1]
Refractive index	1.970 (+.060)[1]
Birefringence	none[1]
Pleochroism	none[1]
Dispersion	.045[1]
Ultraviolet fluorescence	moderate to strong pinkish orange in shortwave[1]

Gadolinium Gallium Garnet (GGG, Gd₃Ga₅O₁₂) is a synthetic crystalline material of the garnet group, with good mechanical, thermal, and optical properties. It is typically colorless. It has a cubic lattice, a density of 7.08 g/cm³ and its Mohs hardness is variously noted as 6.5 and 7.5. Its crystals are produced with the Czochralski method. During production, various dopants can be added for colour modification. The material is also used in fabrication of various optical components and as a substrate material for magneto–optical films (magnetic bubble memory).^[2] It also finds use in jewelry as a diamond simulant. GGG can also be used as a seed substrate for the growth of other garnets such as yttrium iron garnet.^[3]

The Gamma-ray Transients Monitor (a space telescope), which tracks Gamma Ray Bursts (GRBs) and other bright gamma-ray transients with energies ranging from 50 keV to 2 MeV uses Gadolinium Aluminum Gallium Garnet (GAGG) scintillator array (50 mm x 50 mm x 8 mm) as its sensor units.^[4]

See also

• Micro-pulling-down
• Terbium gallium garnet
• Yttrium aluminium garnet

References

1. (Gia), Gemological. Gem Reference Guide. City: Gemological Institute of America (GIA), 1988. ISBN 0-87311-019-6
2. J. F. Greber "Gallium and Gallium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH, Weinheim. doi:10.1002/14356007.a12_163
3. Holm, U.; Sohlstrom, H.; Brogardh, T. (1984). Kersten, Ralf T; Kist, Rainer (eds.). Yig-Sensor Design For Fibre Optical Magnetic Field Measurements. 2nd Intl Conf on Optical Fiber Sensors: OFS'84. Vol. 514. Proc. SPIE 0514, 2nd Intl Conf on Optical Fiber Sensors: OFS'84. pp. 333–6. doi:10.1117/12.945109. S2CID 107371333.
4. Chang, Hsiang-Kuang; Lin, Chi-Hsun; Tsao, Che-Chih; Chu, Che-Yen; Yang, Shun-Chia; Huang, Chien-You; Wang, Chao-Hsi; Su, Tze-Hsiang; Chung, Yun-Hsin; Chang, Yung-Wei; Gong, Zi-Jun; Hsiang, Jr-Yue; Lai, Keng-Li; Lin, Tsu-Hsuan; Lu, Chia-Yu (2022-01-15). "The Gamma-ray Transients Monitor (GTM) on board Formosat-8B and its GRB detection efficiency". Advances in Space Research. 69 (2): 1249–1255. doi:10.1016/j.asr.2021.10.044. ISSN 0273-1177.