Nano-crystallization in LaF3–Na2O–Al2O3–SiO2 glass

Bhattacharyya, Somnath; Höche, Thomas; Hemono, Nicolás; Pascual, María J.; Aken, Peter A. van

doi:10.1016/j.jcrysgro.2009.07.027

Cited by 51 publications

(61 citation statements)

References 21 publications

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“…Fluorine in the glasses appears to be involved in Al-F-Na and La-F bonds, the latter being precursors of LaF 3 nucleation, as discussed in Ref. 82. Thermal treatment of the parent glasses induces the diffusion of fluorine from the glass matrix (Al-F-Na bonds) into the La-F bond enriched nuclei, giving rise to a decrease in the concentration of Al-F-Na and an increase in the number of La-F bonds.…”

Section: Lafmentioning

confidence: 89%

Nanocrystallisation in oxyfluoride systems: mechanisms of crystallisation and photonic properties

Pablos-Martín

Durán

Pascual

2012

International Materials Reviews

154

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Rare earth (RE) doped oxyfluoride glass ceramics possess interesting optical properties with applications in telecommunications and optoelectronics, such as solid state lasers, optical amplifiers, etc. These materials combine the transparency and mechanical and chemical resistance of aluminosilicate glasses with the low phonon energy and facile incorporation of RE ions in the fluoride crystals. The incorporation of RE ions in the crystalline phases enhances the laser emission intensity, a major property of these materials. Transparency is achieved when crystal size is in the nanometric scale, usually below 40 nm, which avoids light scattering. A strict control of the nucleation and crystal growth processes is therefore necessary which requires a deep knowledge of the crystallisation mechanisms. The great activity and publications in this field in the last decades merit a review providing a comparative study of the different nanoglass ceramic systems, their structural and optical characterisation and their main properties and applications. This is the objective of this review paper which includes 232 references. A general discussion on glass nucleation and crystallisation theories and more relevant crystallisation parameters and characterisation techniques are put forward in the first section of the review, focused on nanocrystallisation processes in oxyfluoride systems. In the second section, the principal RE doped glass ceramics are presented. After a general introduction about the luminescence processes, including up-and down-conversion, the behaviour of RE elements in glasses and crystals are discussed. Glass ceramic compositions have been divided as follows: glass ceramics with a glass composition following Wang and Ohwaki's oxyfluoride glass ceramic, 1 ; and glass ceramics with different matrix compositions, arranged by crystalline phases. Relevant properties, mainly optical and laser, are described in each system along with the most relevant applications of these materials.

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Section: Lafmentioning

confidence: 89%

Nanocrystallisation in oxyfluoride systems: mechanisms of crystallisation and photonic properties

Pablos-Martín

Durán

Pascual

2012

International Materials Reviews

154

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“…This is related to the nucleating effect of fluorides which promotes the production of smaller nuclei compared to what happens with lower fluoride content, according to which smaller nuclei should be favored. In fact, it is known that fluorine content in oxyfluoride glasses acts as a nucleating agent and suppresses crystal growth by increasing nuclei quantity (Chen et al, 2007;Bhattacharyya et al, 2009). Pr 3+ singly doped samples showed very similar behavior and only LaF3 crystals precipitate in the glass matrix, and the crystals size is similar to the one obtained for the co-doped samples.…”

Section: X-ray Diffractionmentioning

confidence: 57%

“…The crystal growth exponent at 620°C is p = 0.040 ± 0.005, while for GCs 0.5-1 Pr-Yb the p exponent is p = 0.03 ± 0.01. The very small dependence of crystal growth on the time of heat treatment together with small values for crystal growth exponent p, indicates the presence of an inhibition phenomenon explained in detail in Bhattacharyya et al (2009) and de Pablos-Martín et al (2011. These previous studies showed that La and Si-enriched phase separation droplets are precipitated already during the preparation of the initial glass.…”

Section: X-ray Diffractionmentioning

confidence: 81%

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Transparent Oxyfluoride Nano-Glass Ceramics Doped with Pr3+ and Pr3+–Yb3+ for NIR Emission

et al. 2017

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Pr 3+-Yb 3+ co-doped oxyfluoride glasses and glass-ceramics (GCs) containing LaF3 nanocrystals have been prepared to obtain NIR emission of Yb 3+ ions upon Pr 3+ excitation in the blue region of the visible spectrum. Two different compositions have been tested: 0.1-0.5 Pr-Yb and 0.5-1 Pr-Yb, in addition to Pr 3+ singly doped samples. The crystallization mechanism of the nano-GCs was studied by differential thermal analysis revealing that it occurs from a constant number of nuclei, the crystal growth being limited by diffusion. High-resolution transmission microscopy demonstrated that phase separation acts as precursor for LaF3 crystallization and a detailed analysis of the chemical composition (EDXS) revealed the enrichment in RE 3+ ions inside the initial phase separated droplets, from which the LaF3 crystals are formed. The RE 3+ ions incorporation inside LaF3 crystals was also proved by photoluminescence measurements showing Stark splitting of the RE 3+ ions energy levels in the glass-ceramic samples. Lifetime measurements showed the existence of a better energy transfer process between Pr 3+ and Yb 3+ ions in the GCs compared to the as made glass. The highest value of energy transfer efficiency is 59% and the highest theoretical quantum efficiency is 159%, obtained for GCs 0.1-0.5 Pr-Yb treated at 620°C for 40 h.Keywords: transparent, glass-ceramics, rare-earths, crystallization, down-conversion, solar energy inTrODUcTiOn Solar green energy is one of the emerging fields where rare earth (RE) ions are intensively used to improve silicon solar cells (SSCs) efficiency. In fact, the most important routes to reduce costs and promote the use of solar energy are: decrease refining and crystallization cost of silicon (the most widely used semiconductor), to use less silicon (thinner cells), developing thin films solar cells of less expensive materials (organic, polymeric) and/or improving SSCs efficiency.Currently, many efforts are focused in the modification of the photovoltaic (PV) cells to make them more efficient. The main problem to improve PV energy conversion efficiency is associated with the spectral mismatch between the energy distribution of photons in the incident solar spectrum and the band-gap of silicon (Huang et al., 2013). Therefore, in the last years, solar down-converter materials doped with RE ions, able to convert the blue part of the solar spectrum to the range 980-1050 nm, where silicon presents the best response, are becoming increasingly important (Trupe et al., 2002;Richards, 2006;van der Ende et al., 2009). According to Abrams et al. (2011), a theoretical improvement of SSCs could be as high as 7% for an ideal lossless system; however, improvements (even though smaller than 7%) could be reached with a properly engineered solar converter layer.Among the converter materials, glasses and glass-ceramics (GCs) for PV application are increasingly important thanks to their relatively easy production and engineering and their capability of hosting a great variety of RE ions in different concentrati...

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“…But the complexity of preparation procedure of the crystal growth technique limits theirs practical use. Recently, the controlled crystallization of ferroelectric crystals (BaTiO 3 , PbTiO 3 , LiNbO 3 , NaNbO 3 , KNbO 3 , etc.-perovskite type) in glasses by heat treatment process has been successfully performed and led to the development of ferroelectric materials in glass-ceramics form with pore-free, fine-grained microstructure and specific properties [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Crystallization in Na2O–Nb2O5–Al2O3–SiO2 glass–ceramics system with partial replacement of SnO2 for Al2O3

Kongputhon

Niyompan

Tipakontitikul

2013

Journal of Crystal Growth

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Nano-crystallization in LaF3–Na2O–Al2O3–SiO2 glass

Cited by 51 publications

References 21 publications

Nanocrystallisation in oxyfluoride systems: mechanisms of crystallisation and photonic properties

Nanocrystallisation in oxyfluoride systems: mechanisms of crystallisation and photonic properties

Transparent Oxyfluoride Nano-Glass Ceramics Doped with Pr3+ and Pr3+–Yb3+ for NIR Emission

Crystallization in Na2O–Nb2O5–Al2O3–SiO2 glass–ceramics system with partial replacement of SnO2 for Al2O3

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