Growth and evaluation of large size LGS (La/sub 3/Ga/sub 5/SiO/sub 14/) LGN (La/sub 3/Ga/sub 5.5/Nb/sub 0.5/O/sub 14/) and LGT (La/sub 3/Ga/sub 5.5/Ta/sub 0.5/O/sub 14/) single crystals

Chai, B.H.T.; Lefaucheur, J.; Ji, Yafei; Qiu, Huanguang

doi:10.1109/freq.1998.717983

Cited by 19 publications

(15 citation statements)

References 6 publications

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“…Nowadays, large and high quality crystals can be grown [15,19,45,46]. Beyond that, the composition of the melt determines the properties of the crystals.…”

Section: Langasitementioning

confidence: 99%

“…They enable operation temperatures significantly above 500 • C. The ultimate temperature limits are given by the melting point of langasite and the phase transition of GaPO 4 at 1470 [14,15] and 970 • C [16][17][18], respectively. Another important aspect focussing the interest on langasite is the availability of high quality and large size single crystals manufactured by the Czochralski technique [14,15,19]. GaPO 4 is, in principle, very attractive since shows extremely low losses [20][21][22].…”

Section: High-temperature Piezoelectric Materialsmentioning

confidence: 99%

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High-temperature piezoelectric crystals and devices

Fritze

2011

J Electroceram

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Conventional piezoelectric materials such as quartz are widely used as high precision transducers and sensors based on bulk acoustic waves. However, their operation temperature is limited by the intrinsic materials properties to about 500 • C. High-temperature applications are feasible by applying materials that retain their piezoelectric properties up to higher temperatures. Here, langasite (La 3 Ga 5 SiO 14 ) and compounds of the langasite family are the most promising candidates, since they are shown to exhibit bulk acoustic waves up to at least 1400 • C. The mass sensitivity of langasite resonators at elevated temperatures is about as high as that of quartz at room temperature. Factors limiting potential use of those crystals include excessive conductive and viscous losses, deviations from stoichiometry and chemical instability. Therefore, the objective of this work is to identify the related microscopic mechanisms, to correlate electromechanical properties and defect chemistry and to improve the stability of the materials by e.g. appropriate dopants.Further application examples such as resonant gas sensors are given to demonstrate the capabilities of hightemperature stable piezoelectric materials. The electromechanical properties of langasite are determined and described by a one-dimensional physical model. Key properties relevant for stable operation of resonators are found to be shear modulus, density, electrical conductivity and effective viscosity. In order to quantify their impact on frequency and damping, a general-H. Fritze (B)

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“…Nowadays, large and high quality crystals can be grown [15,19,45,46]. Beyond that, the composition of the melt determines the properties of the crystals.…”

Section: Langasitementioning

confidence: 99%

Section: High-temperature Piezoelectric Materialsmentioning

confidence: 99%

High-temperature piezoelectric crystals and devices

Fritze

2011

J Electroceram

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“…Quartz is stable with temperature and has low acoustic loss, but the low piezoelectric coupling factor makes it difficult to build compact broad band band-pass filters. On the contrary, lithium niobate has a high piezoelectric coupling factor, but the temperature drift is very large, undesirable for band-pass filters used in mobile communication systems [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…At present time only langasite is used for device production, while LGN and LGT are available only in small quantities for property evaluation [2,5,6].…”

Section: Introductionmentioning

confidence: 99%

Comparative study of the mass-loading effect on electrical parameters of gallium phosphate, quartz and langasite resonators

Mateescu

Krispel

Georgescu

et al. 2007

2007 IEEE International Frequency Control Symposium Joint With the 21st European Frequency and Time Forum

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“…LGT grown under Ar [6] [7] or N2 [8] are colorless, while those grown under Ar + O2 are orange [6] [9] [10] [11] and yellow [12] [7]. After vacuum annealing, the LGT samples become colorless and orange colored after air annealing [13] [4] [5].…”

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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Growth and evaluation of large size LGS (La/sub 3/Ga/sub 5/SiO/sub 14/) LGN (La/sub 3/Ga/sub 5.5/Nb/sub 0.5/O/sub 14/) and LGT (La/sub 3/Ga/sub 5.5/Ta/sub 0.5/O/sub 14/) single crystals

Abstract: growth of large diameter 0-7803-4373-5/98/$10.00 0 1998 EEELGS crystals would depend entirely on the ability to minimize the thermal mechanical stress and thus avoid the formation of twinning.

Cited by 19 publications

References 6 publications

High-temperature piezoelectric crystals and devices

High-temperature piezoelectric crystals and devices

Comparative study of the mass-loading effect on electrical parameters of gallium phosphate, quartz and langasite resonators

Color Origins in Langatate Crystals

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