Structure cristalline d'un thiogermanate de plomb á chaïnes infinies (PbGeS3)n

Abstract

PbGeS3 is monoclinic, space group P2a/c with cell constants a = 7.224 (3), b = 10.442 (2), c= 6-825 (2) A,, fl= 105.7 (1) ° and Z=4. The structure was solved by means of Patterson and Fourier syntheses and refined by the least-squares method. The final R value is 0.093. This structure is characterized by GeS4 tetrahedra linked to form infinite (GeS3) 2"-chains, with two tetrahedra per identity period. The chains run parallel to the c axis.

Photoelectric Properties of Crystalline and Glassy PbGeS<sub>3</sub>

“…The transition crystal-glass in lead thiogermanate, similarly to other typical glass formers, for example As 2 S 3 and GeSe 2 [13], is accompanied by diminishing of the conductivity in one-two order of magnitude. Taking into account that the short-range order in crystalline and glassy phases is identical [15], the change of conductivity is conditioned by the disappearance of the long-range order.…”

“…Ge-Pb-S glasses are also X-ray sensitive and do not yield on basic parameters Se and PbO ones, used in X-ray vidicons [12]. The crystalline structure of lead thiogermanate is described in [13,14], the IR and Raman spectra of the ordered and disordered phases were investigated in [15][16][17], and the results of the detailed researches of the absorption edge in a wide range of temperatures are described in [18,19]. From the practical point of view the interest to ternary glasses of Ge-Pb-S system is conditioned by the wide possibilities to use them as the volumetric optical coating for the active devices of integral optics and multifunction devices of semiconductor photonics [20], also as the electrophotographic layers, characterized by substantially smaller (in two times) sizes of maximum charging potentials, and more rapid kinetics of dark semidecay that analogical layers, created on the base of As-S(Se) binary glasses [21].…”

“…Crystals had the appearance of cylinder of 18 -20 mm diameter and till 60 mm long and easily split off on the cleavage plane. These crystals had a monoclinic structure with lattice parameters which corresponded PbGeS 3 compound according to X-ray analysis data [13]. With the purpose to obtain glasses, the fusions of general mass of 8 -10 g cooled down with the rate ~17 K/s.…”

Stangersite, a new tin germanium sulfide, from the Kateřina mine, Radvanice near Trutnov, Czech Republic

“…Although, both cations occurring in the mineral can be present in nature both as divalent and tetravalent state, in the crystal structure of stangersite valence states are combined as divalent (Sn) and tetravalent (Ge). A combination of the coordination tetrahedra of Ge 4+ with coordination pyramids/prisms of Sn 2+ with a lone-electron pair (LEP) character leads to a unique crystal structure of SnGeS 3 , shared only with PbGeS 3 (Ribes et al 1974) in which similar bonding situation occurs.…”

Electronic structure of PbSnS3 and PbGeS3 semiconductor compounds with the mixed cation coordination

“…PbGeS 3 crystal structure projection onto YZ plane with the distinguished chains of [GeS 4 ] tetrahedra (a) and [PbS 5 •E•] -octahedra (b).Lead thiogermanate is formed due to the peritectic reaction at 866 K and crystallizes in the monoclinic structure with the lattice parameters a = 7.224 Å, b = 10.442 Å, c = 6.825 Å, β = 105.7°, Z = 4, space group P2 1 /c[14]. The unit cell of PbGeS 3 contains four bivalent lead (Pb 2+ ) atoms, four tetravalent germanium (Ge 4+ ) atoms and twelve sulfur atoms.…”