High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4

Abstract

X-ray diffraction measurements on the sphalerite-derivatives ZnGa 2 Se 4 and CdGa 2 S 4 have been performed upon compression up to 23 GPa in a diamond-anvil cell. ZnGa 2 Se 4 exhibits a defect tetragonal stannite-type structure ( I42m ) up to 15.5 GPa and in the range from 15.5 GPa to 18.5 GPa the low-pressure phase coexists with a high-pressure phase, which remains stable up to 23 GPa. In CdGa 2 S 4 , we find the defect * Corresponding author, Email: daniel.errandonea@uv.es, Fax: (34) 96 3543146, Tel.: (34) 96 354 4475 tetragonal chalcopyrite-type structure ( I4 ) is stable up to 17 GPa. Beyond this pressure a pressure-induced phase transition takes place. In both materials, the high-pressure phase has been characterized as a defect-cubic NaCl-type structure ( Fm3m ). The occurrence of the pressure induced phase transitions is apparently related with an increase of the cation disorder on the semiconductors investigated. In addition, the results allow the evaluation of the axial compressibility and the determination of the equation of state for each compound. The obtained results are compared with those previously reported for isomorphic digallium sellenides. Finally, a systematic study of the pressure-induced phase transition in twenty-three different sphalerite-related ABX 2 and AB 2 X 4 compounds indicates that the transition pressure increases as the ratio of the cationic radii and anionic radii of the compounds increases.

High-pressure optical and vibrational properties of CdGa2Se4: Order-disorder processes in adamantine compounds

“…10,32 In fact, the c/a ratio of DC structures with Ga and Se, like CdGa 2 Se 4 and HgGa 2 Se 4 , is close to 1.90 while that of the DS structure of ZnGa 2 Se 4 is around 1.98. 21 Therefore, the increase of the c/a ratio with pressure cannot be attributed to the increase of cation disorder on increasing pressure in DC-CdGa 2 Se 4 . However, the much smaller increase of the experimental c/a ratio with pressure than the theoretical one above 6 GPa suggests a partial transformation from the DC to the DS structure above this pressure in good agreeement with our Raman results and with the optical absorption measurements discussed in the next section.…”

High-pressure Raman scattering study of defect chalcopyrite and defect stannite ZnGa2Se4

“…To this respect, while some authors claim that ZnGa 2 Se 4 crystallizes in the tetragonal ordered defect chalcopyrite (DC) structure with space group (SG) I-4 [see Fig. 1(a)] where cations and vacancies are completely ordered, 7,13,15,16,22 other authors report that ZnGa 2 Se 4 crystallizes in the partially disordered tetragonal defect stannite (DS) structure, also known as defect famatinite, with SG I-42 m and higher symmetry than the DC phase [8][9][10][11][12]21,26 [see Fig. 1(b)].…”

“…Electronic mail: rovilap@fis.upv.es b) On leave from CINVESTAV, Departamento de Nanociencia y Nanotecnologıa (Zacatenco, Mexico D. The influence of pressure upon the degree of disorder in the cation sublattice of ZnGa 2 Se 4 has been discussed by various authors. 8,21,22 In Ref. 8, it was shown that DS-ZnGa 2 Se 4 undergoes a phase transition to a sixfold-coordinated disordered rocksalt (DR) by high-pressure (HP) XRD measurements.…”

“…8,21,22 In Ref. 8, it was shown that DS-ZnGa 2 Se 4 undergoes a phase transition to a sixfold-coordinated disordered rocksalt (DR) by high-pressure (HP) XRD measurements. In Ref.…”

“…[1][2][3][4] In particular, ZnGa 2 Se 4 has a high photosensitivity and strong luminescence, 2 can be used for phase change memories, 5 and has been proposed as a candidate for electronic device applications forming part of heterojunction diodes. 6 The properties of ZnGa 2 Se 4 have been characterized by x-ray diffraction (XRD), 7,8 neutron and electron diffraction, [9][10][11][12] extended x-ray absorption fine structure, 13 infrared (IR), 14,15 Raman spectroscopy, [15][16][17][18][19][20][21][22][23][24] and magnetic 25 measurements. To this respect, while some authors claim that ZnGa 2 Se 4 crystallizes in the tetragonal ordered defect chalcopyrite (DC) structure with space group (SG) I-4 [see Fig.…”