X-RAY DIFFRACTION STUDY OF SPHALERITE-CINNABAR PHASE TRANSITION IN Hg1-xCoxS
W. Paszkowicz1,
W. Szuszkiewicz1, K. Szamota-Sadowska1,
J. Domaga3a1, B. Witkowska1,
M. Marczak2, P. Zinn3
1Institute of
Physics PAS, al. Lotników 32, 02-668 Warsaw, Poland, e-mail paszk@ifpan.edu.pl
2The State Mint, ul. Pereca 21, 00-958
Warsaw, Poland
3GeoForschungsZentrum Potsdam,
Telegrafenberg A17, D-14473 Potsdam, Germany
Keywords: semimagnetic semiconductors, phase transition, mercury sulphide, Hg1xCoxS, diffraction at high pressures-high temperatures
Semimagnetic II-VI semiconductors involving substitution of considerable amount of transition metals (Mn, Fe, Co) at cationic sites of tetrahedral structures (zincblende, wurtzite) are a subject of many investigations because of interesting physical properties of such materials. The stable form of mercury sulphide is a-HgS (precursor of the cinnabar structure type). The sphalerite type structure (b - HgS) may be stabilised by partial substitution of Hg atoms by, e.g., Mn [1] or Co [2-3] atoms. For investigation of the pressure and temperature conditions of the b-Hg1xCoxS to a-Hg1xCoxS phase transformation, high-quality single-crystalline Hg1xCoxS samples for high pressure-high temperature studies were grown by the Bridgman method. The Co to Hg ratio was determined by the chemical analysis. X-ray energy-dispersive powder diffraction experiments were performed at non-ambient conditions using an X-ray diffraction press (MAX80) at the F2.1 beamline (HASYLAB at DESY, Hamburg). The p-T range was 0-24 kbar and 27-650oC. For x=0.028, the b-Hg1xCoxS phase starts to transform to the form at about 7 kbar and ends at about 22 kbar. At 650oC, the (considerably sharper) phase transition on uploading occurs at 17 kbar. The variation of lattice parameters with pressure allows for evaluation of compressibility of and phases. The dependence of the transition parameters on cobalt content will be discussed. Results for (Hg,Co)S will be compared with those obtained for (Hg,Mn)S and (Hg,Fe)S solid solutions.
This work was partially supported by the grant No 7-T08A-038-14 from the Committee for Scientific Research (Poland).