Melting Temperature of Al₂O₃ under Pressure

Abstract:

The melting temperature-pressure phase diagram [T_m(P)-P] for corundum (Al₂O₃) is predicted through the Clapeyron equation where the pressure-dependent volume difference is modeled by introducing the effect of surface stress induced pressure. Al₂O₃ has been employed to test the reliability of the model, because of its important role. Al₂O₃ has been extensively investigated because of its widely ranging industrial applications. This includes applications as a refractory material both of high hardness and stability up to high temperatures, as a support matrix in catalysis.

• Periodical: Advanced Materials Research (Volume 549)
• Pages: 745-748
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.549.745
• Online since: July 2012
• Authors: S. Zhang
• Keywords: Phase Transition, Pressure-Dependent, Temperature

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DOI: 10.1002/jctb.280500215

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[10] The necessary parameters in Eq. (6) are as follows: Tm = 2327 K.

[15] Hm = 21. 76 KJ g-atom-1.

[16] Sm=Hm/Tm= 9. 35 Jg-atom-1K-1, Sm=Sel+Spos+Svib, Sel is negligibly small, and Spos=-R[xAln(xA)+ xVln(xV)], where xA= 1/(1+ΔVm) and xV=ΔVm /(1+ΔVm) are the molar fractions of the host material and vacancies, respectively.

[17] and ΔVm is the volume difference between the crystal and corresponding fluid at Tm. As result, Svib= Sm-Spos or Svib » Sm+ R[xAln(xA)+ xVln(xV)].

[23] ΔVm=(VL-VS)/VS, Svib=5. 6 Jg-atom-1K-1, h = 0. 191 nm.

[15] g = 0. 690 Jm-2 , kS =3. 86×10-12 Pa-1 is determined by k =1/B with B =289. 55 GPa being the bulk modulus.

[18] VS = 5. 14 cm3 g-atom.

[18] VL = 6. 16 cm3g-atom-1.

[15] kL =57. 9×10-12 Pa-1 as a first-order approximation under higher pressure, we assume kL » 15kS.

[13] f is calculated through Eq. (2) and f = 4. 5 Jm-2. Fig. 1.