Thermostructural and Elastic Properties of PbTe and Pb0.884Cd0.116Te: A Combined Low-Temperature and High-Pressure X-ray Diffraction Study of Cd-Substitution Effects

Abstract

Rocksalt-type (Pb,Cd)Te belongs to IV–VI semiconductors exhibiting thermoelectric properties. With the aim of understanding of the influence of Cd substitution in PbTe on thermostructural and elastic properties, we studied PbTe and Pb0.884Cd0.116Te (i) at low temperatures (15 to 300 K) and (ii) at high pressures within the stability range of NaCl-type PbTe (up to 4.5 GPa). For crystal structure studies, powder and single crystal X-ray diffraction methods were used. Modeling of the data included the second-order Grüneisen approximation of the unit-cell-volume variation, V(T), the Debye expression describing the mean square atomic displacements (MSDs), <u2>(T), and Birch–Murnaghan equation of state (BMEOS). The fitting of the temperature-dependent diffraction data provided model variations of lattice parameter, the thermal expansion coefficient, and MSDs with temperature. A comparison of the MSD runs simulated for the PbTe and mixed (Pb,Cd)Te crystal leads to the confirmation of recent findings that the cation displacements are little affected by Cd substitution at the Pb site; whereas the Te displacements are markedly higher for the mixed crystal. Moreover, information about static disorder caused by Cd substitution is obtained. The calculations provided two independent ways to determine the values of the overall Debye temperature, θD. The resulting values differ only marginally, by no more than 1 K for PbTe and 7 K for Pb0.884Cd0.116Te crystals. The θD values for the cationic and anionic sublattices were determined. The Grüneisen parameter is found to be nearly independent of temperature. The variations of unit-cell size with rising pressure (the NaCl structure of Pb0.884Cd0.116Te sample was conserved), modeled with the BMEOS, provided the dependencies of the bulk modulus, K, on pressure for both crystals. The K0 value is 45.6(2.5) GPa for PbTe, whereas that for Pb0.884Cd0.116Te is significantly reduced, 33.5(2.8) GPa, showing that the lattice with fractional Cd substitution is less stiff than that of pure PbTe. The obtained experimental values of θD and K0 for Pb0.884Cd0.116Te are in line with the trends described in recently reported theoretical study for (Pb,Cd)Te mixed crystals.

Линейный коэффициент теплового расширения и температура Дебая PbTe при высоких температурах

“…Следует отметить, что и другие современные исследования показали хорошее совпадение с величиной α, полученной в настоящей работе при 300 K. Так в [7], с помощью рентгеновской дифракции найдено, что α = 19.6(6) • 10 −6 K −1 , а в работе [8] (рис. 3).…”

“…Результаты, полученные разными авторами с помощью дифракционных методов для объемных монокристаллов и поликристаллов (порошков) PbTe, лежат в диапазоне от D = 87(1) K [4] (рентгеновская дифрактометрия) до D = 135.9(7) K [7] (рентгеновская дифрактометрия).…”

“…Несмотря на то, что линейный коэффициент теплового расширения (α) и температура Дебая ( D ) относятся к важнейшим характеристикам твердого тела, в настоящее время их значения не являются однозначно определенными для PbTe. Первые исследования теплового расширения PbTe относятся к середине XX века [1,2], и продолжаются в XXI веке [3][4][5][6][7][8]. Большинство известных литературных данных измерены в области низких температур.…”

Electron Paramagnetic Resonance Study of PbSe, PbTe, and PbTe:In Semiconductors Obtained by the Pulsed Laser Deposition Method

“…Due to the metallic conductivity of composites, the skin effect limits the penetration depth of microwave radiation to approximately10 µm, resulting in an asymmetrical (dissonant) shape of the resonance lines [ 24 ]. The most interesting effects related to the influence of electronic properties of semi-magnetic semiconductors on their magnetic behavior are observed in the IV–VI groups of semiconductors, such as PbSe or PbTe [ 25 , 26 , 27 , 28 , 29 ]. Interesting ferromagnetic properties have been observed in many diluted magnetic semiconductors (DMS), e.g., ZnTe + Mn [ 30 ] and CdTe + Cr [ 31 ].…”

Properties of Transition Metals and Their Compounds at Extreme Conditions

“…This Special Issue collects twelve contributions, starting with the paper of Minikayev et al [1]. In this work the authors combine low temperature and high pressure to obtain detailed quantitative information on the evolution of the thermostructural and elastic properties of rock-salt-type crystals of PbTe and Pb 0.884 Cd 0.116 Te.…”