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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on AgSbTe2 by Materials Project

AgSbTe2 is Caswellsilverite-like structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ag1+ is bonded to six Te2- atoms to form AgTe6 octahedra that share corners with six equivalent AgTe6 octahedra, edges with four equivalent AgTe6 octahedra, and edges with eight equivalent SbTe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (3.03 Å) and four longer (3.08 Å) Ag–Te bond lengths. Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with six equivalent SbTe6 octahedra, edges with four equivalent SbTe6 octahedra, and edges with eight equivalent AgTe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (3.03 Å) and four longer (3.08 Å) Sb–Te bond lengths. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ag1+ and four equivalent Sb3+ atoms to form a mixture of edge and corner-sharing TeAg2Sb4 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second Te2- site, Te2- is bonded to four equivalent Ag1+ and two equivalent Sb3+ atoms to form TeAg4Sb2 octahedra that share corners with six equivalent TeAg4Sb2 octahedra and edges with twelve TeAg2Sb4 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgSbTe2 by Materials Project

AgSbTe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ag1+ is bonded to six equivalent Te2- atoms to form AgTe6 octahedra that share corners with six equivalent SbTe6 octahedra, edges with six equivalent AgTe6 octahedra, and edges with six equivalent SbTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. All Ag–Te bond lengths are 3.02 Å. Sb3+ is bonded to six equivalent Te2- atoms to form SbTe6 octahedra that share corners with six equivalent AgTe6 octahedra, edges with six equivalent AgTe6 octahedra, and edges with six equivalent SbTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. All Sb–Te bond lengths are 3.11 Å. Te2- is bonded to three equivalent Ag1+ and three equivalent Sb3+ atoms to form a mixture of edge and corner-sharing TeAg3Sb3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgSbTe2 by Materials Project

AgSbTe2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional and consists of one antimony molecule and one Ag2SbTe4 framework. In the Ag2SbTe4 framework, Ag1+ is bonded in a square co-planar geometry to four Te2- atoms. There are two shorter (3.03 Å) and two longer (3.07 Å) Ag–Te bond lengths. Sb3+ is bonded in a square co-planar geometry to four Te2- atoms. All Sb–Te bond lengths are 3.07 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ag1+, two equivalent Sb3+, and two equivalent Te2- atoms to form TeAg2Sb2Te2 octahedra that share corners with six equivalent TeAg2Sb2Te2 octahedra and edges with eight TeAg4Te2 octahedra. The corner-sharing octahedral tilt angles are 0°. Both Te–Te bond lengths are 3.07 Å. In the second Te2- site, Te2- is bonded to four equivalent Ag1+ and two equivalent Te2- atoms to form TeAg4Te2 octahedra that share corners with six equivalent TeAg4Te2 octahedra and edges with eight TeAg2Sb2Te2 octahedra. The corner-sharing octahedral tilt angles are 0°. Both Te–Te bond lengths are 3.03 Å. In the third Te2- site, Te2- is bonded to two equivalent Ag1+, two equivalent Sb3+, and two equivalent Te2- atoms to form a mixture of edge and corner-sharing TeAg2Sb2Te2 octahedra. The corner-sharing octahedral tilt angles are 0°. Both Te–Ag bond lengths are 3.03 Å. Both Te–Te bond lengths are 3.07 Å. In the fourth Te2- site, Te2- is bonded to six Te2- atoms to form corner-sharing TeTe6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
NASA NTRS2006

Thermoelectric Inhomogeneities in (Ag(sub 1-y)SbTe2)(sub x)(PbTe)(sub 1-x)

A document presents a study of why materials of composition (Ag1 ySbTe2)0.05 (PbTe)0.95 [0< or = y < or = 1] were previously reported to have values of the thermoelectric figure of merit [ZT (where Z = alpha(sup 2)/rk, alpha is the Seebeck coefficient, r is electrical resistivity, k is thermal conductivity, and T is absolute temperature)] ranging from <1 to >2. In the study, samples of (AgSbTe2)0.05(PbTe)0.95, (Ag0.67SbTe2)0.05 (PbTe)0.95, and (Ag0.55SbTe2)0.05(PbTe)0.95 were prepared by melting followed, variously, by slow or rapid cooling. Analyses of these samples by x-ray diffraction, electron microscopy, and scanning-microprobe measurements of the Seebeck coefficient led to the conclusion that these materials have a multiphase character on a scale of the order of millimeters, even though they appear homogeneous in x-ray diffraction and electron microscopy. The Seebeck measurements showed significant variations, including both n-type and p-type behavior in the same sample. These variations were found to be consistent with observed variations of ZT. The rapidly quenched samples were found to be less inhomogeneous than were the furnace-cooled ones; hence, rapid quenching was suggested as a basis of research on synthesizing more nearly uniform high-ZT samples.

Snyder, G. Jeffrey↗