Ultrasound propagation and binding in solids

Abstract

Measurement of sound wave velocity and attenuation by the ultrasonic pulse-echo technique are used to obtain insight into the nature of weak interatomic binding forces which are present or develop in certain materials. In particular, anomalies are found in both the elastic and anelastic properties in the vicinity of the martensitic phase transformations which occur in TiNi andIndium-thallium alloys. Considerable differences found between the elastic moduli of the two phases of TiNi are shown to arise Mainly from a variation in the free carrier density. Previously reported elastic constant data of some fcc indium-thallium alloysAre complemented by the present results and an overall picture of the compositional dependence of the elastic properties of theseAlloys in both the tetragonal and cubic phases are provided. Zirconia can be forced into a cubic structure by the addition of more than 7 mole % yttria: elastic constant data of two zirconia-yttria solid solutions, technologically important materials, provides a basis for the discussion of the stability of the cubic phase. Finally, on the basis of an evaluation of the elastic moduliof arsenic, a pronounced layer-type crystal, the ultrasonic wave propagation characteristics in this material are extensively compared and contrasted with those of the other two rhombohedral elemental semimetals antimony and bismuth, neither of which are themselves layer-like. The elastic wave propagation in antimony and bismuth is shown to differ not only in degree but also in kind from that in arsenic which exhibits the characteristics expected for a layer-like crystal. The weak binding forces in each of the materials studied are shown to play a dominant role in their elastic behaviour.