An X-Ray Method for Accurate Determination of Lattice Strains of Crystals

Abstract

A simple x‐ray strainmeter is described which enables us to determine small lattice strains of crystals with the sensitivity of 2×10⁻⁶ even in the region of 45° of Bragg angle. The principal feature of this apparatus lies in the large camera radius of 2630 mm. The strainmeter permits not only determination of the thermal expansion at 1°C but also measurement of piezoelectric constants of minute crystals where conventional resonance‐antiresonance methods cannot be used. The practical application of this apparatus for detection of small spontaneous lattice strain, say 3′40″ of pure shear x_y of Fe–I‐boracite, which has recently been found to be ferroelectric in its low temperature form, is demonstrated.