Elastic constants of corundum up to 1825 K

Goto, Tomoyo; Anderson, Orson L.; Ohno, Ichiro; Yamamoto, Shigeru

doi:10.1029/jb094ib06p07588

Cited by 203 publications

(118 citation statements)

References 28 publications

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“…Adiabatic and isothermal bulk moduli do coincide with each other at zero temperature only, K S always being larger than K T at any finite temperature. In the figure, for instance, empty circles do represent adiabatic bulk modulus values as measured at zero pressure by Goto et al 83 with the rectangular parallelepiped resonance method. The QHA also offers a way to compute the adiabatic bulk modulus from the isothermal one, given that:…”

Section: Effect Of Thermal Pressurementioning

confidence: 99%

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al₂O₃

Erba

Maul

Demichelis

et al. 2015

Phys. Chem. Chem. Phys.

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The thermochemical behavior of α-Al 2 O 3 corundum in the whole temperature range 0-2317 K (melting point) and under pressures up to 12 GPa is predicted by applying ab initio methods based on the density functional theory (DFT), the use of a local basis set and periodic-boundary conditions. Thermodynamic properties are treated both within and beyond the harmonic approximation to the lattice potential. In particular, a recent implementation of the quasi-harmonic approximation, in the CRYSTAL program, is here shown to provide a reliable description of the thermal expansion coefficient, entropy, constant-volume and constant-pressure specific heats, and temperature dependence of the bulk modulus, nearly up to the corundum melting temperature. This is a remarkable outcome suggesting α-Al 2 O 3 to be an almost perfect quasi-harmonic crystal. The effect of using different computational parameters and DFT functionals belonging to different levels of approximations on the accuracy of the thermal properties is tested, providing a reference for further studies involving alumina polymorphs and, more generally, quasiionic minerals.

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Section: Effect Of Thermal Pressurementioning

confidence: 99%

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al₂O₃

Erba

Maul

Demichelis

et al. 2015

Phys. Chem. Chem. Phys.

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“…The room temperature shear modulus measured here is in good agreement with the literature data for the shear modulus of polycrystalline Al 2 O 3 calculated from single crystal data to be 162.5-163.2 GPa (Ahrens 1995). Goto et al (1989) . The channel 1 shear modulus shows a temperature dependence despite the rod being outside the furnace.…”

Section: Shear Modulus Of Torsion Rodsmentioning

confidence: 99%

Shear modulus, heat capacity, viscosity and structural relaxation time of Na2O–Al2O3–SiO2 and Na2O–Fe2O3–Al2O3–SiO2 melts

Falenty

Webb

2010

Phys Chem Minerals

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The configurational heat capacity, shear modulus and shear viscosity of a series of Na 2 O-Fe 2 O 3 -Al 2 O 3 -SiO 2 melts have been determined as a function of composition. A change in composition dependence of each of the physical properties is observed as Na 2 O/(Na 2 O ? Al 2 O 3 ) is decreased, and the peralkaline melts become peraluminous and a new charge-balanced Al-structure appears in the melts. Of special interest are the frequency dependent (1 mHz-1 Hz) measurements of the shear modulus. These forced oscillation measurements determine the lifetimes of Si-O bonds and Na-O bonds in the melt. The lifetime of the Al-O bonds could not, however, be resolved from the mechanical spectrum. Therefore, it appears that the lifetime of Al-O bonds in these melts is similar to that of Si-O bonds with the Al-O relaxation peak being subsumed by the Si-O relaxation peak. The appearance of a new Al-structure in the peraluminous melts also cannot be resolved from the mechanical spectra, although a change in elastic shear modulus is determined as a function of composition. The structural shear-relaxation time of some of these melts is not that which is predicted by the Maxwell equation, but up to 1.5 orders of magnitude faster. Although the configurational heat capacity, density and shear modulus of the melts show a change in trend as a function of composition at the boundary between peralkaline and peraluminous, the deviation in relaxation time from the Maxwell equation occurs in the peralkaline regime. The measured relaxation times for both the very peralkaline melts and the peraluminous melts are identical with the calculated Maxwell relaxation time. As the Maxwell equation was created to describe the timescale of flow of a mono-structure material, a deviation from the prediction would indicate that the structure of the melt is too complex to be described by this simple flow equation. One possibility is that Al-rich channels form and then disappear with decreasing Si/Al, and that the flow is dominated by the lifetime of Si-O bonds in the Al-poor peralkaline melts, and by the lifetime of Al-O bonds in the relatively Si-poor peralkaline and peraluminous melts with a complex flow mechanism occurring in the mid-compositions. This anomalous deviation from the calculated relaxation time appears to be independent of the change in structure expected to occur at the peralkaline/peraluminous boundary due to the lack of charge-balancing cations for the Al-tetrahedra.

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“…The temperature at which the heat capacity approaches 3R or only slightly varying with temperature depends on the bond strength (or elastic constants), and melting point of the material and varies widely for different materials (or the Lindemann relationship). 8 For example, the heat capacities of soft metals such as silver and copper become independent of temperature near room temperature (Deybe temperature for silver and copper is -48°C and 70°C, respectively), 9 while oxide ceramics such as alumina reaches a constant heat capacity around 1043°C, 10 and strong covalently bonded diamond reaches this temperature at 1587°C. 8 In this report, the heat capacity for PZT95/5(1.8Nb) and PSZT ceramics were measured between -100 °C to 300 °C (data reported from -50°C to 300°C), which is much higher than the operating temperature range for the quantum mechanical model.…”

Section: (B) Heat Capacity and Enthalpymentioning

confidence: 99%

Thermal properties of PZT95/5(1.8Nb) and PSZT ceramics.

Rae¹,

Corelis²,

Yang³

et al. 2006

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Thermal properties of niobium-modified PZT95/5(1.8Nb) and PSZT ceramics used for the ferroelectric power supply have been studied from -100 °C to 375°C. Within this temperature range, these materials exhibit ferroelectric-ferroelectric and ferroelectric-paraelectric phase transformations. The thermal expansion coefficient, heat capacity, and thermal diffusivity of different phases were measured. Thermal conductivity and Grüneisen constant were calculated at several selected temperatures between -60°C and 100°C. Results show that thermal properties of these two solid solutions are very similar. Phase transformations in these ceramics possess first order transformation characteristics including thermal hysteresis, transformational strain, and enthalpy change. The thermal strain in the high temperature rhombohedral phase region is extremely anisotropic. The heat capacity for both materials approaches to 3R (or 5.938 cal/(g-mole*K)) near room temperature. The thermal diffusivity and the thermal conductivity are quite low in comparison to common oxide ceramics, and are comparable to amorphous silicate glass. Furthermore, the thermal conductivity of these materials between -60°C and 100°C becomes independent of temperature and is sensitive to the structural phase transformation. These phenomena suggest that the phonon mean free path governing the thermal conductivity in this temperature range is limited by the lattice dimensions, which is in good agreement with calculated values. Effects of small compositional changes and density/porosity variations in these ceramics on their thermal properties are also discussed. The implications of these transformation characteristics and unusual thermal properties are important in guiding processing and handling procedures for these materials.

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Elastic constants of corundum up to 1825 K

Cited by 203 publications

References 28 publications

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al₂O₃

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al₂O₃

Shear modulus, heat capacity, viscosity and structural relaxation time of Na2O–Al2O3–SiO2 and Na2O–Fe2O3–Al2O3–SiO2 melts

Thermal properties of PZT95/5(1.8Nb) and PSZT ceramics.

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Elastic constants of corundum up to 1825 K

Cited by 203 publications

References 28 publications

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al2O3

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al2O3

Shear modulus, heat capacity, viscosity and structural relaxation time of Na2O–Al2O3–SiO2 and Na2O–Fe2O3–Al2O3–SiO2 melts

Thermal properties of PZT95/5(1.8Nb) and PSZT ceramics.

Contact Info

Product

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Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al₂O₃

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al₂O₃