Untersuchung des Systems Ag₂Se‐Ag₂S

Abstract

Das System Ag2SeAg2S wurde mittels differential‐thermischer, Röntgen‐Phasen‐ und Mikrostrukturanalyse sowie Bestimmung der Dichte und der Mikrohärte untersucht. Es wurden Gleichgewichtsproben verwendet, die bei Temperung bei 200, 400 und 500° erhalten wurden. Das System Ag2SeAg2S ist ein polythermischer (nicht quasibinärer) Schnitt des dreifachen Diagramms AgSeS. Es ist durch das Vorhandensein von Mischkristallen im ganzen Konzentrationsintervall gekennzeichnet mit Ausnahme der Zusammensetzung die 50% Ag2S entspricht. Ein peritektischer Zerfall wird bei 835° und einer Zusammensetzung von 60 Mol‐% Ag2S beobachtet.

Probable metal–insulator transition in Ag4SSe

“…Thus, we may conclude that the transition point for our sample is 358.2 K, with negligible small hysteresis. This value is within the limits reported for Ag 4 SSe: 373 ± 5 [2], 367 ± 2 [20], and 348 K [21]. The transition enthalpy values are reproduced very well separately for heating (8.5, 8.5, 8.6 J g À1 ) and cooling (9.2, 9.1, 9.1 J g À1 ), but differ from one another by 7%.…”

“…The transition points for Ag 4 SSe shown in Fig. 1 of [3] are dispersed within the limits of ±2.5 K. Heat treatment is known to affect the hardness of all solid solutions in the Ag 2 S-Ag 2 Se system, including Ag 4 SSe [2]. As for the electrical conductivity and magnetic susceptibility, we did not find the references about their changes after heat treatment for Ag 4 SSe, but they are known to change for end members Ag 2 S and Ag 2 Se, with particularly large effects in Ag 2 Se [31].…”

“…For DSC, this point was clearly indicated in the title of report [3]. Other works were carried out with using derivatograph (MOM, Hungary) that operates only above room temperature [2,21,33]. X-ray diffraction is usually applied to the detection of phase homogeneity in the solid solutions under investigation, when only the unit cell parameters are of interest, without careful examination of extra weak reflections.…”

“…Sulfur-rich high-temperature corner is occupied with a solid solution based on c-Ag 2 S. Below the solidus lines, cubic (b) Ag 2 S x Se 1Àx solid solution occupies the whole field of compositions with complete miscibility, because both end members of the series, b-Ag 2 S and b-Ag 2 Se, are isostructural cubic phases. The line of a-b transition was investigated in [2,3]. Below the a-b border, there is a miscibility gap between the sulfur-rich monoclinic solid solution and selenium-rich orthorhombic solid solution, both named a. Two-phase region was found to be between Ag 2 S 0.4 Se 0.6 and Ag 2 S 0.3 Se 0.7 , which is shown in Fig.…”

“…The Ag 4 SSe was concluded to be a specific individual phase [2] and was used as the end member of several pseudobinary and pseudoternary systems [5][6][7][8][9][10][11][12][13][14]. Alternatively, it is considered to be an ordinary member of the monoclinic Ag 2 S-type solid solution [3,4].…”