New LGT crystal for ultra-stable resonators

Boy, J.J.; Allani, M.; Batis, Narjès Harrouch; Bel, O.; Cambon, O.; Haines, J.; Roumanille, P.; Lebbou, Kheirréddine; Cabane, H.; Hassouni, A.; Pécheyran, Christophe

doi:10.1109/eftf.2014.7331430

Cited by 3 publications

(3 citation statements)

References 8 publications

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“…The spectrum of the air-annealed LGT sample V exhibits an absorption band at 3430 cm −1 , which is absent in the spectra of unannealed LGT samples I, II, III-1 and IV. The absorption band at 3430 cm −1 was attributed to the Ga-OH link [10].…”

Section: Resultsmentioning

confidence: 99%

Effects of the Langatate crystal quality on the resonance frequency stability of bulk acoustic wave resonators

Allani

Batis

Laroche

et al. 2018

Advances in Applied Ceramics

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In the time and frequency domain, we need ultrastable crystal resonators embedded in Ultra Stable Oscillators (USO), working at 10 MHz and exhibiting excellent short-term stabilities. Up to now, the quartz crystal fulfils its function. But, Langatate La 3 Ga 5.5 Ta 0.5 O 14 (LGT) piezoelectric crystal seems to allow better performances with high quality material. The applications of this domain require high-quality material with reproducible properties. The LGT crystal is grown by the Czochralski method. Its physical and chemical properties and specificities of this growth process induce defects. They can react as ionic and electronic charge carriers and generate conductive losses. To assess the quality of the LGT crystal, we recorded the UV-VIS and IR transmission spectra and measured the electrical resistivity. At least, Y-cut resonators have been designed and manufactured to study the quality of the 10 MHz resonance, particularly its Q-factor, directly linked to the stability of the USO. We studied the effect of air annealing on the resonance frequency quality.

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Section: Resultsmentioning

confidence: 99%

Effects of the Langatate crystal quality on the resonance frequency stability of bulk acoustic wave resonators

Allani

Batis

Laroche

et al. 2018

Advances in Applied Ceramics

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“…To maintain electroneutrality, cation and anion vacancies will form. If 0 < x < 0.5 GaTa'' (Gallium rich melt composition), the crystal will be negatively charged and electroneutrality will be ensured by oxygen vacancies according to the quasi chemical reactions (2).…”

Section: Electron Color Centersmentioning

confidence: 99%

“…In fact, these applications require homogeneous crystals with reproducible physical properties. For that, before manufacturing acoustic devices (sensors, transducers, actuators or ultra-stable resonators), we control the quality of the crystal, using accurate techniques to reveal structural defects [2] [3]. Indeed, point defects, such as impurities and oxygen vacancies significantly affect the physicochemical properties (optical, electrical, piezoelectric…) and induce the crystal color.…”

Section: Introductionmentioning

confidence: 99%

Color Origins in Langatate Crystals

Allani¹,

Batis²,

Nehari³

et al. 2017

Int. Ann. Sci.

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A B S T R A C TLangatate 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 O 2-→ Fe 3+ and/or Fe 3+ -Fe 3+ 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, (V O .. , 2e′) x , are discussed. And, finally, point defects changes the band gap of langatate, leading to extend the absorption to visible light regions.

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