Color Origins in Langatate Crystals

  • Maroua Allani FEMTO-ST Institute
  • Narjès Batis INSAT, Université de Carthage, BP 676, 1080 Tunis cedex, Tunisia
  • Abdeldjelil Nehari ILM Institute, UCBL, 69000 Lyon, France
  • Hugues Cabane Cristal Innov, 73800 Sainte-Hélène du Lac, France
  • Kheirreddine Lebbou ILM Institute, UCBL, 69000 Lyon, France
  • Christophe Pecheyran LCABIE - IPREM –Université de Pau - 64053 Pau Cedex 9, France
  • Corine Reibel Institut Charles Gerhard, Université de Montpellier, 34000 Montpellier, France
  • Jean-Jacques Boy FEMTO-ST Institute, UFC, CNRS, ENSMM, UTBM, 25000 Besançon, France


Langatate La3Ga5.5Ta0.5O14 is piezoelectric crystal from langasite family, commonly grown by Czochralski method from Ir crucible. Langatate crystals of different colors (colorless, orange, green) have been studied by optical spectroscopy in UV-Visible (200 – 800 nm) and IR (7000 – 1000 cm-1) ranges. Furthermore, the effects of irradiation by ultraviolet laser source (λ=266 nm) and post-growth annealing in N2+O2 atmosphere have been investigated. The yellow-orange is mainly due to an absorption centered in the ultraviolet that extends into the blue of the visible spectrum (250-500 nm). The IR optical absorption spectra of Langatate crystals exhibit an absorption band at 5370 cm-1. It seems linked to a point defect responsible for color. The intensity of the absorption band at 3430 cm-1 increases after annealing in oxygen containing atmosphere. We have discussed phenomenon that can occur simultaneously in langatate crystals and produce very similar colors which are related to structural defects. First, metal ions impurities (as Iron, Titanium…), whose presence is previously confirmed by femtosecond laser ablation coupled with ICP-MS spectroscopy, can contribute to langatate color. Second, ultraviolet absorption leads us to think about charge transfer phenomenon such as O2- → Fe3+ and/or Fe3+-Fe3+ pair transitions. Third, the irradiation by ultraviolet (λ=266 nm) laser source locally color the langatate sample by the creation of color centers. Origins of color centers, particularly those related to oxygen vacancies, ( , 2e′)x, are discussed. And, finally, point defects changes the band gap of langatate, leading to extend the absorption to visible light regions.

Keywords: color, color centers, charge transfer, ESR spectrum, fs LA-ICP-MS coupling, impurities, langasite family crystals, optical spectrometry.


Download data is not yet available.


[1]               R. C. Smythe, R. C. Helmbold, G. E. Hague, and K. A. Snow, “Langasite, langanite, and langatate bulk-wave Y-cut resonators,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 47, no. 2, pp. 355–360, Mar. 2000.

[2]               J. J. Boy et al., “New LGT crystal for ultra-stable resonators,” in European Frequency and Time Forum (EFTF), 2014, 2014, pp. 75–78.

[3]               M. Allani et al., “How to qualify LGT crystal for acoustic devices?,” in Frequency Control Symposium & the European Frequency and Time Forum (FCS), 2015 Joint Conference of the IEEE International, 2015, pp. 100–105.

[4]               I. A. Kaurova, G. M. Kuz’micheva, V. B. Rybakov, A. B. Dubovskii, and A. Cousson, “Composition, structural parameters, and color of langatate,” Inorg. Mater., vol. 46, no. 9, pp. 988–993, 2010.

[5]               G. M. Kuz’micheva et al., “The color of langatate crystals and its relationship with composition and optical properties,” Cryst. Res. Technol., vol. 47, no. 2, pp. 131–138, 2012.

[6]               O. A. Buzanov, E. V. Zabelina, and N. S. Kozlova, “Optical properties of lanthanum-gallium tantalate at different growth and post-growth treatment conditions,” Crystallogr. Rep., vol. 52, no. 4, pp. 691–696, Jul. 2007.

[7]               H. Kawanaka, H. Takeda, K. Shimamura, and T. Fukuda, “Growth and characterization of La3Ta0.5Ga5.5O14 single crystals,” J. Cryst. Growth, vol. 183, no. 1, pp. 274–277, Jan. 1998.

[8]               B. Chai, J. L. Lefaucheur, Y. Y. Ji, and H. Qiu, “Growth and evaluation of large size LGS (La3Ga5 SiO14) LGN (La3Ga5.5Nb0.5 O14) and LGT (La3Ga5.5Ta0.5 O14) single crystals,” in Proceedings of the 1998 IEEE International Frequency Control Symposium (Cat. No.98CH36165), 1998, pp. 748–760.

[9]               G. M. Kuz’micheva, E. A. Tyunina, E. N. Domoroshchina, V. B. Rybakov, and A. B. Dubovskii, “X-ray diffraction study of La3Ga5.5Ta0.5O14 and La3Ga5.5Nb0.5O14 langasite-type single crystals,” Inorg. Mater., vol. 41, no. 4, pp. 412–419, Apr. 2005.

[10]             G. M. Kuzmicheva, E. N. Domoroschina, V. B. Rybakov, A. B. Dubovsky, and E. A. Tyunina, “A family of langasite: growth and structure,” J. Cryst. Growth, vol. 275, no. 1–2, pp. e715–e719, Feb. 2005.

[11]             G. M. Kuz’Micheva et al., “Point defects in langatate crystals,” Crystallogr. Rep., vol. 54, no. 2, pp. 279–282, 2009.

[12]             H. Takeda, K. Sugiyama, K. Inaba, K. Shimamura, and T. Fukuda, “Crystal Growth and Structural Characterization of New Piezoelectric Material La3Ta0.5Ga5.5O14,” Jpn. J. Appl. Phys., vol. 36, no. 7B, pp. L919, Jul. 1997.

[13]             I. A. Kaurova, G. M. Kuz’micheva, and A. B. Dubovskii, “Physicochemical properties of La3Ga5.5Ta0.5O14,” Inorg. Mater., vol. 46, no. 10, pp. 1131–1136, Oct. 2010.

[14]             T. Taishi, N. Bamba, K. Hoshikawa, and I. Yonenaga, “Single crystal growth of langataite (La3Ta0.5Ga5.5O14) by vertical Bridgman (VB) method along [2 1¯ 1¯0] in air and in an Ar atmosphere,” J. Cryst. Growth, vol. 311, no. 1, pp. 205–209, Dec. 2008.

[15]             H. Kimura, S. Uda, O. Buzanov, X. Huang, and S. Koh, “The effect of growth atmosphere and Ir contamination on electric properties of La3Ta0.5Ga5.5O14 single crystal grown by the floating zone and Czochralski method,” J. Electroceramics, vol. 2, no. 20, pp. 73–80, 2008.

[16]             O. A. Buzanov, N. S. Kozlova, E. V. Zabelina, A. P. Kozlova, and N. A. Siminel, “Optical transmission spectra and electrical properties of langasite and langatate crystals as dependent on growth conditions,” Russ. Microelectron., vol. 40, no. 8, pp. 562–566, 2011.

[17]             M. Alani et al., “Influence of the growth and annealing atmosphere on the electrical conductivity of LTG crystals,” Opt. Mater., vol. 65, pp. 99–102, 2017.

[18]             E. Fritsch and G. R. Rossman, “An update on color in gems. Part 1: Introduction and colors caused by dispersed metal ions,” Gems Gemol., pp. 126–139, 1987.

[19]             E. Fritsch and G. R. Rossman, “An Update on Color in Gems. Part 2: Colors Involving Multiple Atoms and Color Centers,” Gems Gemol., vol. 24, no. 1, pp. 3–15, Mar. 1988.

[20]             H. H. Tippins, “Charge-transfer spectra of transition-metal ions in corundum,” Phys. Rev. B, vol. 1, no. 1,pp. 126, 1970.

[21]             V. S. Balitsky and O. V. Balitskaya, “The amethyst-citrine dichromatism in quartz and its origin,” Phys. Chem. Miner., vol. 13, no. 6, pp. 415–421, 1986.

[22]             J. Ferguson and P. E. Fielding, “The origins of the colours of yellow, green and blue sapphires,” Chem. Phys. Lett., vol. 10, no. 3, pp. 262–265, 1971.

[23]             S. M. Mattson and G. R. Rossman, “Ferric iron in tourmaline,” Phys. Chem. Miner., vol. 11, no. 5, pp. 225–234, 1984.

[24]             E. N. Domoroshchina, “Effect of Growth Conditions on the Composition, Structure, and Properties of Langasite-Family Crystals,” in Extended Abstract of Cand. Sci.(Chem.) Dissertation, pp. 24, 2005.

[25]             C.-Y. Chung, R. Yaokawa, H. Mizuseki, S. Uda, and Y. Kawazoe, “First principles calculation of La 3 Ta 0.5 Ga 5.5 O 14 crystal with acceptor-like intrinsic point defects,” J. Appl. Phys., vol. 108, no. 11, pp. 113505, 2010.

How to Cite
M. Allani, “Color Origins in Langatate Crystals”, Int. Ann. Sci., vol. 2, no. 1, pp. 12-19, Jun. 2017.
Research Article