Title :
Precision volume measurements on silicon spheres [Avogadro constant]
Author :
Sacconi, Attilio ; Panciera, Renzo ; Pasin, Walter
Author_Institution :
Ist. di Metrol. G. Colonnetti, CNR, Torino, Italy
fDate :
4/1/1997 12:00:00 AM
Abstract :
In the determination of the Avogadro constant NA, use is made of silicon spheres as volume-density standards, where volume measurements play a critical role. After various changes in the experimental apparatus and in the measurement procedure, new volume measurements have been made on the two IMGC spherical standards. Present results confirm the 1994 results within 0.15×10-6 in volume. Preliminary data are also presented on the thermal expansivity of four silicon spheres. The average linear coefficient of thermal expansion at 20°C is a=2.567×10-6/K-1, with a sphere-to-sphere variability of up to 2.5×10-8/K -1
Keywords :
constants; elemental semiconductors; measurement standards; shape measurement; silicon; thermal expansion measurement; thermal variables measurement; volume measurement; 20 C; Avogadro constant; IMGC spherical standards; Si; Si spheres; linear coefficient of thermal expansion; precision volume measurements; roundness measurement; sphere-to-sphere variability; thermal expansivity; volume-density standards; Computational Intelligence Society; Density measurement; Impurities; Instruments; Lattices; Measurement standards; Optical filters; Silicon; Thermal expansion; Volume measurement;
Journal_Title :
Instrumentation and Measurement, IEEE Transactions on
