Precision volume measurements on silicon spheres Avogadroconstant

• Published in: IEEE transactions on instrumentation and measurement Vol. 46; no. 2; pp. 584 - 587
• Main Authors: Sacconi, A, Panciera, R, Pasin, W
• Format: Journal Article
• Language: English
• Published: 01.04.1997
• ISSN: 0018-9456
• DOI: 10.1109/19.571924

In the determination of the Avogadro constant N(A), 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 0.15x10(-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 deg C is a=2.567x10(-6)/K(-1), with a sphere-to-sphere variability of up to 2.5x10(-8)/K (-1)