title: Application of calorimetry on a chip to high-pressure materials.
abstract: Silicon micromachined calorimeters ("calorimeter on a chip") are used to measure heat capacities and phase transition enthalpies for thin film, single crystal, and powder samples (5-500 mug). The technology is thus compatible with the small samples produced in multianvil and large diamond anvil cells. Techniques for handling small samples and attaching them to the calorimetric devices have been developed. Initial data illustrate application to CoO and to Fe(2)SiO(4) olivine and spinel, a quenched high pressure phase metastable at ambient conditions. The calorimetric entropy of the olivine-spinel transition in Fe(2)SiO(4) (-16 +/- 5 J/mol.K) is in good agreement with that calculated from phase equilibrium data (-14 +/- 3 J/mol.K). A magnetic transition in iron silicate spinel, detected previously by Mossbauer spectroscopy, is seen in the calorimetric signal.
authors.affiliation: Thermochemistry Facility and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit, University of California, Davis, CA 95616, USA. anavrotsky@ucdavis.edu
authors.forename: Alexandra
authors.initials: A
authors.lastname: Navrotsky
authors.forename: Maria
authors.initials: M
authors.lastname: Dorogova
authors.forename: Frances
authors.initials: F
authors.lastname: Hellman
authors.forename: David W
authors.initials: DW
authors.lastname: Cooke
authors.forename: Barry L
authors.initials: BL
authors.lastname: Zink
authors.forename: Charles E
authors.initials: CE
authors.lastname: Lesher
authors.forename: Juliana
authors.initials: J
authors.lastname: Boerio-Goates
authors.forename: Brian F
authors.initials: BF
authors.lastname: Woodfield
authors.forename: Brian
authors.initials: B
authors.lastname: Lang
mesh_terms: D002151:Calorimetry / Q000295:instrumentation* / Q000379:methods*; D003035:Cobalt / Q000737:chemistry; D058085:Iron Compounds / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D011312:Pressure; D012825:Silicon / Q000737:chemistry; D013696:Temperature
chemical_list: D058085:Iron Compounds; D008903:Minerals; D010087:Oxides; D003035:Cobalt; D010100:Oxygen; C060728:cobalt oxide; D012825:Silicon