Precise interferometric measurements at single crystal silicon yielding thermal expansion coefficients from 12 °C to 28 °C and compressibility.

Interferometrically measured length changes of a silicon gauge block were performed under well defined environmental conditions. Special efforts - described in this paper - were made to reduce the uncertainties of the measurements. The used silicon crystal is of high purity and dislocation free. Expansion coefficients were obtained from thermal induced length changes in the range from 12 degreesC to 28 degreesC with uncertainties from about 0.01 % to 0.03 %. This corresponds to an uncertainty reduction by a factor of ten compared with earlier studies in this temperature range. The length change of the silicon gauge block induced by pressure variations from vacuum to atmospheric pressure provides a value for the compressibility of crystalline silicon with an uncertainty of about 1.5 %. This directly measured compressibility slightly differs from literature data obtained from indirect measurements via ultrasonic wave velocities. The possible nature of this deviation is briefly discussed.