Ba 3 Yb(BO 3 ) 3 single crystals: Growth and spectroscopic characterization
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Güell Enginyeria i Materials Electrònics (EME), Departament d’Electrònica, Universitat de Barcelona, E-08028 Barcelona, Catalunya, Spain
Jna. Gavaldà, M. Aguiló, and F. Díaz Física i Cristal⭈lografia de Materials (FiCMA), Universitat Rovira i Virgili (URV), Campus Sescelades, E-43007 Tarragona, Catalunya, Spain (Received 7 February 2008; accepted 13 June 2008)
We obtained Ba3Yb(BO3)3 single crystals by the flux method with solutions of the BaB2O4–Na2O–Yb2O3 system. The evolution of the cell parameters with temperature shows a slope change at temperatures near 873 K, which may indicate a phase transition that is not observed by changes appearing in the x-ray powder patterns or by differential thermal analysis (DTA). The evolution of the diffraction patterns with the temperature shows incongruent melting at temperatures higher than 1473 K. DTA indicates that there is incongruent melting and this process is irreversible. Ba3Yb(BO3)3 has a wide transparency window from 247 to 3900 nm. We recorded optical absorption and emission spectra at room and low temperature, and we determined the splitting of Yb3+ ions. We used the reciprocity method to calculate the maximum emission cross section of 0.28 × 10−20 cm2 at 966 nm. The calculated lifetime of Yb3+ in Ba3Yb(BO3)3 is rad ⳱ 2.62 ms, while the measured lifetime is ⳱ 3.80 ms.
I. INTRODUCTION
In recent years, borate single crystals have been arousing increasing interest because of their potential as nonlinear optical materials and laser hosts. Many articles have been published on crystal growth and the discovery of new nonlinear optical borate crystals that can incorporate laser-active ions in their matrix to create a selfdoubling material.1–8 Recently, laser crystals containing Yb3+ ions have attracted greater interest because their simple electronic structure has only two energy levels, the ground level and an excited level, separated by energy of about 10,000 cm−1. Thus, there is no excited-state absorption, nor upconversion processes, and their quantum defect is small.9 Ba3Yb(BO3)3 is a new noncentrosymmetrical crystal with the space group P63cm and cell parameters a ⳱ b ⳱ 9.411(1) and c ⳱ 17.481(5) Å.10 Because of the high content of Yb3+ in Ba3Yb(BO3)3 and the lack of a sym-
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0313 2512
http://journals.cambridge.org
J. Mater. Res., Vol. 23, No. 9, Sep 2008 Downloaded: 13 Mar 2015
metry center, this phase could be interesting as selfdoubling material.11 In the present work, we study the growth conditions of Ba3Yb(BO3)3 crystals in the BaB2O4–Na2O–Yb2O3 system. The thermal evolution of the crystals obtained is characterized by x-ray powder diffraction and by differential thermal analysis (DTA). The linear thermal expansion tensor is also obtained. The final aim of this study is to characterize the optical properties of these crystals by measuring of the optical absorption and emission at room temperature and low temperature and to confirm that they are good candidates
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