Mössbauer study of phase transitions under high hydrostatic pressures. I. The phase transition of Mg2Sn

Abstract

Experimental results of the hydrostatic pressure influence on Mössbauer spectrum parameters are obtained over the pressure range including the area of structural phase transition. A linear increase of the Mössbauer effect probability (recoilless fraction) is accompanied by a linear decrease of the electron density at tin nuclei within the pressure range foregoing the phase transition. The electric resistance and the recoilless fraction of the new phase of Mg2Sn are lower, but the electron density at tin nuclei is greater than the initial phase ones. Hydrostatic conditions allow to fix clearly the diphasic transition area and to determine the influence of the pressure on the Mössbauer line position and on the recoilless fraction of the high pressure phase. The phase transition heat Q = 415 cal mol−1 is calculated using recoilless fractions of the high and low pressure phases at 25 kbar. The present results are qualitatively and quantitatively different from the results, obtained at nonhydrostatic conditions.

Mössbauer Study of Phase Transitions under High Hydrostatic Pressures II. The Phase Transition of SnTe

“…The decrease of the distance of 5p electrons from the nuclei, expressed by the increasing quadrupole splitting of the Mossbauer spectrum of SnO with increasing pressure [14], agrees with this interpretation of the above-mentioned common characteristic. The same behaviour has been observed in Mg,Sn under pressure [15].…”

Giant Pressure‐Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

“…A total increase of ~15% from the minimum at 3.2 GPa is observed at 4.2 GPa. As SnTe undergoes a pressure-induced structural phase transition between 1.8 and 4.1 GPa, [16][17][18][19][20] this change in the electrical resistance correlates well with this structural transition. Energy-dispersive X-ray diffraction (EDXRD) data obtained insitu provides corresponding evidence of this structural phase transition.…”

“…However, concerns about the toxicity of lead-based chalcogenides such as PbTe, PbSe, PbS, and other related materials limits their large scale applications and this has lead to alternatives with similar properties being sought out. One such alternative is SnTe which crystallizes in the cubic Fm-3m structure [16][17][18][19][20] and has a similar band structure to PbTe suggesting promising TE behavior. [7,8,[21][22][23] However, pure SnTe has poor TE performance because of intrinsic Sn vacancies which lead to a high thermal conductivity and a low Seebeck coefficient.…”

“…[24] In recent years, chemical doping and alloying have been attempted to enhance the performance, which have yielded ZT values as high as 1.4. [3][4][5][6]25,26] Pure SnTe undergoes a pressure-induced structural phase transition to an orthorhombic phase, [16][17][18][19][20] which has recently received more attention to clarify the convoluted mixture of phases that have been observed. [20] High-pressure and high-temperature (HP-HT) conditions have also been used to synthesize TE compounds with improved transport properties.…”

On the Mechanism of Magnesium Storage in Micro- and Nano-Particulate Tin Battery Electrodes

“…The IS value of 1.847 9 mm s −1 is ascribable to cubic c-Mg 2 Sn [21,25]. In agreement with the well-known fluorite-type structure of c-Mg 2 Sn, tin atoms are eight-fold coordinated by magnesium and twelve-fold coordinated by tin second neighbors, which is in contrast with the use of less and more directional covalent bonds in β-Sn and agrees with the significantly lower isomer shift relative to β-Sn (Figure 2a).…”