The perovskite-like yttrium aluminate YAlO₃ (orthorhombic structure) reveals a polarized laser beam and because of it, is an excellent host for solid state lasers scintillators and acustooptic materials as well as Q-switch.

Comparing with YAG, the single crystals of YAP can be grown faster, have a smaller core and more favorable distribution coefficient for rare-earth dopants; it seems to be useful for laser host.

The YAP:Co single crystals were grown by the Czochralski method using iridium crucibles (54 mm in diameter and 52 mm in height) and iridium afterheater. Oxypuller 05-03 equipment made by Cyberstar (France) was used. As raw materials: Y₂O₃ (5N), Al₂O₃ (5N) and CoO + Co₂O₃ (4.85N) were used. The concentration of Co²⁺ ions was 0.22 at. %, 0.30 at. %, and 0.40 at. %. The crystals were grown under N₂ atmosphere with a gas flow rate of 0.4 l/min. The pulling rate was between 1 - 2 mm/h and the rotation rate was between 10 rpm and 20 rpm. An automatic diameter control was carried out using Cyberstar programme, in which weight differential was maintained constant. Sartorius balance was used to control the weight of the growing crystal.

The obtained single crystals up to 25 mm in diameter and 60 mm in length were free of macroscopic defects and inclusions of other phases.

The samples for measurements were taken from each crystal by slicing for a wafer ~1mm thickness, and double sides polishing. A part of this wafers were annealed in reduction atmospheres:

1) in hydrogen, at 1200⁰ C for 10 min,

2) in vacuum, at 1750⁰ C for 5 hour,

3) first in hydrogen at 1200⁰ C for 10 min and next in vacuum, at 1750⁰ C for 5 hour.

After annealing the wafers were slowly cooled down to room temperature.

The electron spectroscopy XPS shows the chemical composition is in agreement with a nominal composition of compound. A very low contamination of carbon was detected. The narrowest core level lines were observed for the sample annealed in hydrogen which was colourless.

References

1. S.Baccaro, K. Blażek, F.de Notaristefani, P. Maly, J.A. Mares, R. Pani "Scintillation properties of YAP:Ce", Nuclear Instruments and Methods in Physics Research A 361 (1995) 209-215,

2. G. Neuroth, F. Wallrafen, “Czochralski growth and characterisation of pure and doped YAlO₃ single crystals”, Journal of Crystal Growth 198/199 (1999) 435-439,

3.J.B. Shima, A. Yoshikawa, M. Nikl, N. Soloviev, J. Pejchal, D.H. Yoon, T. Fukuda, “Growth and characterization of Yb³⁺-doped YAlO₃ fiber single crystals grown by the modified micro-pulling-down method”, Journal of Crystal Growth 256 (2003) 298–304,

4. A.J. Wojtowicza, P. Bruyndonckx, W. Drozdowski, Z. Gałązka, J. Głodo, T. Łukasiewicz, P. Szupryczyński, S. Tavernierc, M. Wiśniewska, D. Wiśniewski, “Traps and recombination centers in YAlO₃:Ce, Co”, Nuclear Instruments and Methods in Physics Research A 486 (2002) 482–485,

5. Andrzej J. Wojtowicz, “Rare-earth-activated wide bandgap materials for scintillators”, Nuclear Instruments and Methods in Physics Research A 486 (2002) 201–207,

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