The results of ultrasonic, sonic and infrasonic experiments in high-Tc superconductors (HTSC) are reviewed. Some other related fields of investigation are also mentioned.

https://iopscience.iop.org/article/10.1088/0953-2048/6/3/001/pdf

Ultrasonic and related experiments in high-Tc superconductors

Ultrasonic velocity measurements have been undertaken by the pulse transmission technique using YBaCuO samples prepared by the melt-powder-melt-growth (MPMG) process over a temperature range of 80–300 K. It has been observed that the sample exhibits a very high value of Young's and rigidity moduli, thereby indicating that the material is an excellent one from the point of view of its mechanical strength. Further, the Young's modulus apart from exhibiting a hump at around 120 K, is found to increase continuously with decreasing temperature. In the superconducting phase, however, the modulus is found to remain almost constant. It has been concluded that the observed elastic behavior, to a large extent, is analogous to that of normal oxide materials. In order to understand how far the experimentally observed behavior deviates at 120 K, the elastic moduli of the sample were also estimated theoretically and compared with the empirical values.

Elastic behavior of a YBaCuO sample prepared by the MPMG method

Effect of annealing on the dynamic Young׳s modulus E of ultrafine-grained (UFG) and microcrystalline (MC) copper obtained by combined severe plastic deformation (SPD) including repeated hydrostatic extrusion and drawing (UFG copper) or only repeated drawing (MC copper) is investigated. It is established that the Young׳s modulus in the SPD-prepared UFG and MC samples exceeds that in the coarse-grained fully annealed (CGFA) samples by 10% to 20%. Subsequent isothermal annealing at elevated temperatures between 90 and 470 °С leads to a sharp decrease of the Young׳s modulus for annealing temperatures above 210 °С. After annealing at 410 °С, the value of E reaches its minimal value that is 35% lower than E in CGFA samples (total change in E is about 50% of the initial value). Further annealing at higher temperatures leads to some increase in the Young׳s modulus. It is shown that the unusual behavior of the Young׳s modulus is caused by the formation of the 〈111〉 axial drawing texture in the SPD-treated samples which is replaced by the 〈001〉 annealing texture during the post-SPD heat treatments.

Unusual Young׳s modulus behavior in ultrafine-grained and microcrystalline copper wires caused by texture changes during processing and annealing

The results of research on the plasticity and strength of a wide class of metal oxide perovskite-like compounds which have the property of high-temperature superconductivity or which can be used as base compounds for making high-temperature superconductors (HTSCs) are systematized and presented from a unified point of view. The mechanical properties of materials with different morphology—single crystals, polycrystals, and composites,—measured by different methods of mechanical testing in the low-temperature, room-temperature, and high-temperature regions, are discussed. The characteristic defects of the crystal structure for these compounds are considered, the crystallography of two modes of plastic deformation—slip and twinning—is described, and the stress-induced structural rearrangement of the twin structure that appears at a high-temperature phase transformation is discussed. The features of plastic deformation and fracture of metal oxide materials due to structural microdefects (dislocations, impurities, twin and grain boundaries) and macrodefects (voids, cracks, heterophase inclusions) are noted, and the role of heavy-cation diffusion in the kinetics of high-temperature deformation is discussed. The influence of structural phase transformations and the superconducting transition on the mechanical properties of metal oxides is considered. This review is a continuation of a review of the elastic and acoustic properties of HTSCs published earlier by the authors in Fiz. Nizk. Temp. 21, 475 (1995) [Low Temp. Phys. 21, 367 (1995)].

Plasticity and strength of metal oxide high-temperature superconductors (Review)

The effect of oxygen loss on the luminescence of YBa_2Cu_3O_(7-x) has been investigated by cathodoluminescence (CL) in the scanning electron microscope (SEM) and by Raman microprobe measurements. The results herein indicate that a CL band at 530 nm is related to oxygen loss rather than to impurity phases such as Y_2O_3 formed in the material by electron irradiation in the SEM.

/pdf/cathodoluminescence-and-microraman-analysis-of-oxygen-loss-39gghx3g77.pdf

Cathodoluminescence and microRaman analysis of oxygen loss in electron irradiated YBa2Cu3O7−x

The temperature dependences of acoustic properties of nanostructured and polycrystalline zirconium are investigated in the temperature range of 100–340 K. The effect of severe plastic deformation and subsequent annealing on key parameters of the Koiwa–Hasiguti acoustic relaxation in zirconium is studied in detail. It is established that, due to intensive plastic deformation, the relaxation strength considerably increases, and the temperature and the width of the corresponding relaxation peak systematically decrease with reduction of the mean grain size in the samples. Annealing leads to a partial recovery of the relaxation strength and the peak temperature back to the initial values in undeformed samples, but the width of the relaxation peak shows an additional decrease. The majority of the effects observed can be explained by changes in dislocation subsystems of the samples during intensive plastic deformation and annealing. An influence of a random scatter of the relaxation time on the main parameters of the Koiwa–Hasiguti peak is established using the statistical analysis based on the lognormal distribution. It is shown that the parameter β of the lognormal distribution determines the width, height, and asymmetry of the peak and also allows estimating the relaxation strength from the peak height. An algorithm for retrieving the parameter β from experimental data is presented.

/pdf/change-of-parameters-of-the-koiwa-hasiguti-dynamic-4r2k34mt3g.pdf

Change of Parameters of the Koiwa–Hasiguti Dynamic Dislocation Relaxation in Nanostructured and Polycrystalline Zirconium after Severe Plastic Deformation and Annealing

In the temperature range from 6 to 300 K, the resistivity ρ, microhardness HV, dynamic Young’s modulus E and logarithmic decrement δ (vibration frequency ∼75 kHz) have been studied in In–4.3 at.% Cd polycrystalline alloy. The measurements were carried out during cooling and heating of samples at a rate of 1 K min−1. A hysteresis with boundaries Tmin≅150 K and Tmax≅290 K is observed in the temperature dependences ρ(T), E(T) and δ(T). The maximum relative values of the hysteresis loops are Δρ/ρ≅0.1, ΔE/E≅0.25 and Δδ/δ≅0.25. Within the hysteresis region, the characteristics measured are unstable and their values change slowly with time at fixed temperatures. The hysteresis has not been registered in HV(T), but the derivative d/dT Hv(T) has an essential feature in the temperature interval Tmin<T<Tmax. The anomalies mentioned are indicative of the existence of some low-temperature structural transformation of hysteretic type controlled by complicated kinetics with large relaxation times. The structure and the physical and mechanical properties of pure In remain stable in the temperature range studied and reveal no anomalies mentioned. It is also shown that the alloy In–4.3 at.% Cd has sufficiently high plastic compliance and internal friction in a wide range of low temperatures that qualify it as a high damping material.

Low-temperature structure transformation in In–Cd solid solutions

Effect of silver concentration on electric and magnetic properties of HTS composites YBa 2 Cu 3 O x -Ag

The temperature and magnetic field dependences of low-frequency ultrasound absorption in niobium single crystals of different purity have been investigated in the temperature range 2 to 12 K. It is shown for the first time that the unusual sound absorption behaviour, which was previously observed in niobium at the transition from the superconducting (s-) to the normal (n-) state (via the mixed (m-) state), can be explained by the presence of an acoustic relaxation peak at these temperatures and by an anomalous shift of this peak during the s-m-n transition. A theory of the relaxation based on the model of resonant interaction of sound with dislocation kink chains, generated in screw dislocations under the action of thermoelastic stresses during rapid sample cooling, is suggested.



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Dislocation mechanism of acoustic anomalies in superconducting niobium

The temperature dependence of the logarithmic decrement δ and dynamic Young’s modulus E in niobium single crystals of high purity is investigated in a wide interval of low temperatures 3 K⩽T⩽300 K Measurements are made by means of a two-component composite vibrator method under excitation of longitudinal vibrations with a frequency of 88 kHz and a relative amplitude of the acoustic strain varying in the range 5×10−9 e0c and their transformation with temperature are investigated in detail Analysis shows that the nonlinear effects are due to the breakaway of ultrasonically excited dislocations from 

L. N. Pal-Val

Papers

Change of Parameters of the Koiwa–Hasiguti Dynamic Dislocation Relaxation in Nanostructured and Polycrystalline Zirconium after Severe Plastic Deformation and Annealing

Low-temperature structure transformation in In–Cd solid solutions

Effect of silver concentration on electric and magnetic properties of HTS composites YBa 2 Cu 3 O x -Ag

Dislocation mechanism of acoustic anomalies in superconducting niobium

Nonlinear acoustic effects arising from dislocations in niobium single crystals