Application of calorimetry on a chip to high-pressure materials.
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.
Navrotsky
Alexandra
A
Thermochemistry Facility and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit, University of California, Davis, CA 95616, USA. anavrotsky@ucdavis.edu
Dorogova
Maria
M
Hellman
Frances
F
Cooke
David W
DW
Zink
Barry L
BL
Lesher
Charles E
CE
Boerio-Goates
Juliana
J
Woodfield
Brian F
BF
Lang
Brian
B
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
D058085:Iron Compounds; D008903:Minerals; D010087:Oxides; D003035:Cobalt; D010100:Oxygen; C060728:cobalt oxide; D012825:Silicon