Topic
Debye model
About: Debye model is a research topic. Over the lifetime, 7462 publications have been published within this topic receiving 133987 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, the elastic constants of single-crystal BeO were measured to determine their magnitude relative to those of other hexagonal materials and to enable a correlation with related properties.
Abstract: The five elastic constants of single-crystal BeO were measured to determine their magnitude relative to those of other hexagonal materials and to enable a correlation with related properties. The pulse-echo method was used. The stiffness constants are c11 4.70, c12 1.68, c13 1.19, c33 4.94, and c44 1.53 × 1012 dynes/cm2. These were related to the Young's, shear, and bulk moduli of polycrystalline BeO, the Debye temperature, and the repulsion term for the crystal energy.
52 citations
TL;DR: In this paper, a Kawai-type multianvil apparatus was used to obtain high-quality diffraction pattern against grain growth of Mg2SiO4 ringwoodite at temperatures from 300 to 2000 K and pressure from 15 to 24 GPa.
Abstract: [1] Unit cell volumes of Mg2SiO4 ringwoodite were measured at temperatures from 300 to 2000 K and pressure from 15 to 24 GPa and at a temperature of 300 K and pressure from 0 to 21 GPa. The measurements were conducted using a Kawai-type multianvil apparatus that is equipped with an oscillation system to obtain high-quality diffraction pattern against grain growth. We obtained the following relations and parameters describing the pressure-volume-temperature relations of Mg2SiO4 ringwoodite. The unit cell volume of Mg2SiO4 ringwoodite at 0 GPa and 300 K is 524.8(1) A3 (values in parentheses are errors). Fixing the isothermal bulk modulus to 182 GPa, its pressure derivative is 4.6(2). The thermal expansion coefficient at 0 GPa is α0 = 2.57(9) × 10−5 + 1.42(8) × 10−8 (T − 300) K−1, where T is absolute temperature in K, and its logarithmic volume dependence, Anderson-Gruneisen parameter, is 6.9(4). The temperature derivative of the isothermal bulk modulus is (∂KT/∂T) = −0.029(1) GPa K−1. The Debye temperature, Θ, is 846(26) K. The Gruneisen parameter and its logarithmic volume dependence are 1.93(3) and 3.5(3), respectively. The adiabatic temperature gradient in the mantle largely depends on temperature. That in the model Mg2SiO4 mantle increases from 0.29 to 0.40 K km−1 when temperature increases from 1600 to 2000 K.
52 citations
TL;DR: The magnetic properties of the quaternary oxides Ba2LnTaO6 (Ln = Y or lanthanides) are reported in this article, where powder x-ray diffraction measurements and Rietveld analysis show that they have an ordered perovskite structure and are monoclinic with space groups P21/n or cubic with space group Fmm.
Abstract: Magnetic properties of the quaternary oxides Ba2LnTaO6 (Ln = Y or lanthanides) are reported. Their powder x-ray diffraction measurements and Rietveld analysis show that they have an ordered perovskite structure and are monoclinic (Ln = La-Tb) with space group P21/n or cubic (Ln = Y, Dy-Lu) with space group Fmm. Magnetic susceptibilities of Ba2LnTaO6 were measured. All compounds in this work are paramagnetic down to 5 K. Ba2EuTaO6 and Ba2SmTaO6 show Van Vleck paramagnetism; their spin-orbit coupling constants are determined to be 331 cm-1 and 287 cm-1, respectively. 151Eu Mossbauer measurements for Ba2EuTaO6 were carried out at 12, 100, 200 and 300 K. The Eu ion is in the trivalent state, and the symmetry of the Eu site is distorted from the octahedral symmetry. The Debye temperature of Eu3+ was determined to be 335 K from the temperature dependence of the absorption area of intensity curves.
51 citations
TL;DR: In this article, an extended x-ray absorption fine structure (EXAFS) analysis of the thermoelectric clathrates Eu{sub 8}Ga{sub 16}Ge{sub 30} and Sr{sub 6} Ga{sub 14.5] Ge{sub 15.5} was presented, showing that the lattice is quite stiff with a high correlated Debye temperature.
Abstract: We present a detailed extended x-ray absorption fine structure (EXAFS) analysis of the thermoelectric clathrates Eu{sub 8}Ga{sub 16}Ge{sub 30} and Sr{sub 8}Ga{sub 16}Ge{sub 30}, both of which have an unusually low thermal conductivity attributed to a 'rattler' motion of the filler atoms Eu and Sr. The EXAFS results show that the Ga/Ge lattice is quite stiff with a high correlated Debye temperature {approx}400 K. Eu is on-center in the site 1 cage but off-center (0.445{+-}0.020 A) in the large cage called the Eu2 site. The results for Sr are similar, but {approx}75% are off-center 0.40{+-}0.05 A and {approx}25% are on-center in the Sr2 site. Both results are in reasonable agreement with diffraction results. The temperature dependence of the nearest neighbor pair distribution widths yield low Einstein temperatures (80{+-}10 and 100{+-}10 K for Eu1 and Sr1, respectively, and 95{+-}10 and 125{+-}10 K for the shortest Eu2-Ga/Ge and Sr2-Ga/Ge pairs). In contrast, the more distant Eu2/Sr2-Ga/Ge pair distributions within the Eu2/Sr2 cage are strongly disordered even at low T, indicating considerable local disorder. This indicates that the off-center Eu or Sr atom is bonded to the side of the site 2 cage. This has two important implications for the thermal conductivity: itmore » increases the coupling between the 'rattler' vibrations and the lattice phonons and it introduces a symmetry-breaking large mass defect.« less
51 citations
TL;DR: In this article, single crystals of cesium have been grown by a modified Bridgman technique and the adiabatic elastic constants were measured at 4.2° and 78°K by an ultrasonic pulse echo technique.
51 citations