Te SOLID SOLUTION IN A BROAD TEMPERATURE RANGE

P 38 ISSRNS 2012: Abstracts / Synchrotron Radiation in Natural Science Vol. 11, No 1 – 2 (2012)

X-RAY STUDIES OF THERMAL PROPERTIES OF Pb

Cd

Te SOLID SOLUTION IN A BROAD TEMPERATURE RANGE

R. Minikayev^1∗, E. Dynowska¹, T. Story¹, A. Szczerbakow¹, A.M.T. Bell², D. Trots³, and W. Szuszkiewicz¹

1Institute of Physics, Polish Academy of Sciences, Al. Lotnik´ow 32/46, PL–02668 Warsaw, Poland

2HASYLAB at DESY, Notkestr. 85 , D–22607 Hamburg, Germany

3Universit¨at Bayreuth, Universit¨atsstr. 30, D–95440 Bayreuth, Germany

Keywords: synchrotron radiation, thermal expansion, structure refinement, high temperature, low temperature

∗e-mail : minik@ifpan.edu.pl

The Pb1−xCdxTe solid solution constitutes an attractive system for developing of the mid-IR op- toelectronic or the thermo-electric devices based on quantum dots. These applications are powered by extremely low solubility of both materials [1] re- sulting from the difference in their crystal struc- ture — rock salt (RS) for PbTe and zinc-blende (ZB) for CdTe. However, it was difficult to get a Pb1−xCdxTe uniform composite and only recently the metastable single crystals were obtained by self- selecting vapour growth (SSVG) method followed by a rapid quenching of resulting solid solutions [2, 3].

An access to new materials of high-quality made it possible to perform the X-ray diffraction measure- ments in a wide temperature range.

The previously performed high-temperature diffraction studies permitted us to correct a part of the relevant phase diagram [4]. Because of a huge difference between the expansion coefficient for CdTe [5] and PbTe [6] resulting from their different crystal structure the structure properties of Pb1−xCdxTe crystals in a broad temperature range were also of great interest. The goal of the present work was to study the structure properties of Pb1−xCdxTe solid solution at low and high tem- peratures and to get also new information about the temperature behavior of lattice parameters, and the thermal expansion coefficient values.

Single bulk Pb_1−xCd_xTe crystals (with x ≤ 0.11) obtained by SSVG method at the In- stitute of Physics of the Polish Academy of Sciences in Warsaw were the object of present investigations.

In situ low- and high-temperature X-ray diffraction measurements were performed at the B2 beamline (Hasylab/DESY), using the Debye-Scherrer geom- etry. The samples were prepared as a mixture of powdered Pb1−xCdxTe crystals and fine diamond powder (in the capacity of an internal standard), and placed in a thin-wall quartz or glass capillary, rotating inside a graphite heater or the cryostat during measurements. The Rietveld method, was used for the structural analysis.

The analysis of the results accomplished with the Rietveld refinement demonstrated a monotonous evolution of the lattice parameter with tempera- ture. Thermal expansion of Pb1−xCdxTe crystals with the rock salt structure has been measured and analyzed for the first time at low temperatures.

Temperature evolution of the linear expansion co- efficient of Pb1−xCdxTe is similar to that corre- sponding to PbTe and its value is positive at all temperatures under investigation. Linear expan- sion coefficient increases with increasing Cd con- tent in Pb1−xCdxTe in comparison to relevant val- ues corresponding to PbTe. Information concern- ing the Pb1−xCdxTe solid solution phase diagram and CdTe solubility limit in PbTe for x < 0.1 and T < 1100 K will also be shown and discussed.

Acknowledgments: This work has been partially sup- ported by the European Community’s Seventh Frame- work Programme (FP7/2007 – 2013) under grant agree- ment no. 226716 and by the European Union within the European Regional Development Fund, through grant Innovative Economy (POIG.01.01.02-00-108/09).

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