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Elastic Constants of Polycrystalline BeO as a Function of Pressure and Temperature
Author(s) -
SOGA NAOHIRO
Publication year - 1969
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1969.tb09176.x
Subject(s) - crystallite , thermodynamics , thermal , materials science , wurtzite crystal structure , superposition principle , crystal (programming language) , mineralogy , chemistry , physics , metallurgy , quantum mechanics , zinc , computer science , programming language
The sound velocities of polycrystalline BeO and their pressure and temperature derivatives were determined by a pulse superposition method. The derivatives found from the measurements at pressures up to 2 kbars and near 25° are: (∂ ul /∂P) T = 6.48×10 −3 km/s kbars, ∂ S /∂P) T = 0.33×10 −3 km/s kbars, ∂ L /∂T) P =−2.8×10 −4 km/s deg, and ∂ S /∂P) T =−2.0×10 −4 km/s deg. The very low value of ∂ S /∂P) T is anomalous for crystalline solids but may be expected from the crystal structure in view of similar anomalous behavior found in other solids with the wurtzite structure. The Grüneisen parameter calculated from the pressure derivatives of sound velocities was small compared with the Grüneisen parameter obtained from thermal properties. This result seems to indicate that the thermal expansivity of BeO does not change with temperature in proportion to the specific heat at low temperatures.