Thermodynamic properties of MgSiO3ilmenite from vibrational spectra

✍ Scribed by Anne M. Hofmeister; Eiji Ito

• Publisher: Springer-Verlag
• Year: 1992
• Tongue: English
• Weight: 997 KB
• Volume: 18
• Category: Article
• ISSN: 0342-1791
• DOI: 10.1007/bf00200965

✦ Synopsis

Unpolarized infrared (IR) reflectance spectra for MgSiO3 ilmenite taken from a single-crystal and from a densly packed polycrystalline sample possessed all eight peaks mandated by symmetry between 337 and 850 cm-5. Polarizations were inferred from intensity differences between the two samples. IR peak positions differ by up to 250 cm-~ from recent calculations, but on average are within 11%. Heat capacity Cp calculated from these data by using a Kieffer-type model are within the experimental uncertainty of calorimetric measurements from 170 to 700 K. Outside this range, calculated Cp is probably accurate within a few percent, based on recent results for garnets. Calculated entropy is only slightly less accurate, giving S o (298.15 K) as 54.1 +_ 0.5 J/ mol-K, which is 10% lower than recent estimates based on phase equilibria. The slope of the phase boundary between ilmenite and perovskite is used to predict S o (298.15 K) of perovskite as 58.7 + 1.4 J/tool-K, which is 10% lower than previous values.