Peculiarities of the Frequency Dependences of the Dislocation Decrement of Ultrasound Attenuation for Ionic Crystals with Radiation Defects and Impurities

An analysis of frequency dependences of dislocation decrement of ultrasound attenuation Δd(f) behavior in KBr, LiF and NaCl crystals was performed in experiments with variable temperature T and dislocation density Λ of crystals, as well as with variations in dose of X-irradiation in the studied samples. It is shown that, unlike the experiments with variable T and Λ, where the high-frequency asymptotes of the Δd(f) curves were represented by families of straight lines, in the experiments with X-irradiated samples, a fundamental difference is observed – they merge into a single straight line. Within the framework of the key relationship of the Granato-Lücke theory, which describes the behavior of dynamic and structural characteristics based on the data of the post-resonance region of the curves Δd(f), obtained within the framework of the amplitude-independent internal friction method, the justification of the obtained results of experiments with the variables T, Λ and the X-irradiation dose was made. A prediction was made that the approximation of the Granato-Lücke formula, which describes the behavior of high-frequency asymptotes for irradiated samples, should also work for experiments with a variable impurity composition of the studied crystals. A comparison of the obtained Δd(f)dependences on pure KCl and KCl + Ba crystals (10 – 2 wt. %) was made, and the predicted effect of high-frequency asymptotes merging into a solid line in experiments on crystals with variable impurity composition is proved. It is proved that the approximation of the formula of the Granato-Lücke theory describes the anomalous behavior of the high-frequency asymptotes of the Δd(f) curves for experiments with a variable concentration of any weak stoppers of the Friedel type.