Lithium niobate (LiNbO₃) and lithium tantalate (LiTaO₃) are among the most important and most widely used materials of coherent and nonlinear optics, as well as acoustics. High degree of uniformity and reproducibility has become the foundation of technology for manufacturing high-quality crystals, absorbed by many suppliers around the world. However, the above areas do not limit the use of LiNbO₃ and LiTaO₃ due to their unique piezoelectric and ferroelectric properties. One promising application of crystals is the design of electromechanical transducers for precision sensors and actuators. In this respect, the high thermal stability of the piezoelectric and mechanical properties, the lack of hysteresis and creep make it possible to create electromechanical converters with wide operating temperature range, that is beyond the capability of commonly used ferroelectric ceramics. The main advantage of LiNbO₃ and LiTaO₃ over other single-crystal piezoelectrics is ferroelectric domain structure regulation toward targeted impact on the device characteristics. One of the most striking examples of electromechanical transducer design through domain engineering is the formation of a so-called bidomain ferroelectric structure in crystal. It represents a single-crystalline plate with two macrodomains with opposite directions of spontaneous polarization vectors separated by a charged domain wall. High switching fields make inversion domains stable at temperatures up to 1000 °C. This review summarizes the main achievements in the formation of bidomain structure and near surface inversion domains in LiNbO₃ and LiTaO₃ crystals. We present the domain structure virtualization methods in crystals and non-destructive methods for controlling the domain boundary position. The report contains a comparative analysis of the methods for forming inversion domains in crystals, and the patterns and technological control methods of the domain structure are discussed. The basic physical models have been proposed in the literature to explain the effect of the inversion domains formation. In the present paper we outline what one sees as strengths and weaknesses of these models. The strategies of crystallographic cut selection to create devices based on bidomain crystals are briefly discussed. We provide examples of the implementation of devices based on bidomain crystals such as actuators, sensors, acoustic transducers, and waste energy collection systems.

Materials properties affecting EC device operation are discussed based on an analytically tractable model of a layered EC refrigerator. Special attention was paid to thermal and interface thermal resistances. Estimates of the average cooling power of a stacked MEMS-based EC refrigerator were made.

The influence of thermocycling annealing processes on the oxygen ordering degree (order parameter) in theYBa₂Cu₃O_7-δ single crystals have been studied. It was determined that an increase in the critical temperature of the onset of the transition to the superconducting state during step annealing procedures is consistent with decrease of the σ_с/σ_аb parameter. This fact indicates the redistribution of the electronic density between the Cu(2)O₂ and Cu(1)O_1-d structurally-inhomogeneous planes, due to the formation of the oxygen long-range ordering in the O(4)—Cu(1)—O(4) linear groups along the (b) crystal structure axis of the unit cell, and removal of the oxygen defects in the square nets of the Cu(2)O₂ planes. The existence of a critical value of the conductivity anisotropy σс/σаb, below which its behavior does not correlate with the change of Т_с, has been proved. In this case, the increase of Тс and the orthorhombic distortion of the crystal structure at the isothermal annealing processes occur due to the amplification of the «interlayer» interaction between the Cu(2)О₂ and Cu(1)О_1-δ planes. As a result, the contribution of the Cu(1)О_1-δ chain layers in the electronstate density on the Fermi level increases. These layers could be the superconducting ones by means of the Cooper pairs tunneling from the Cu(2)О₂ planes, forming the induced superconductivity there.

The article provides an overview of known luminescent materials based on calcium gallate CaGa₂O₄, emitting in the visible and infrared (IR) spectral regions. IR phosphors have not been studied much, but their practical application is of interest. The solid-phase method was used to obtain CaGa₂O₄ samples activated with rare-earth ions Yb³⁺. The structural and luminescent properties of the composition CaGa₂O₄ : Yb³⁺ were studied. When CaGa₂O₄ : Yb³⁺ was excited by radiation with a wavelength of 940 and 980 nm, luminescence was recorded in the range of 980—1100 nm. Based on data on the structure of electronic levels in Yb³⁺ ions, it is concluded that excitation and radiation occur directly in Yb³⁺ ions with the passive participation of the base lattice. Three maximums at a wavelength were recorded on the luminescence spectra: 993 nm, 1025 nm, 1080 nm. The radiation in these bands is due to optical transitions of electrons from the excited to the ground state in Yb³⁺ ions. The dependence of the luminescence intensity in the 993 nm band on the concentration of Yb³⁺ activator ions was studied. It found that the introduction of the phosphor ions Na⁺ increases the intensity of the infrared luminescence. An optimal composition of the phosphor (Ca_1-x-yYb_xNa_y)Ga₂O₄ is proposed, at which the luminescence intensity in the range of 980—1100 nm is maximum.

The economic feasibility of using aluminum as a conductive material is explained by the favorable ratio of its cost to the cost of copper. It is also important that the cost of aluminum for many years remains virtually unchanged.

When using conductive aluminum alloys for the manufacture of thin wire, winding wire, etc. Certain difficulties may arise in connection with their insufficient strength and a small number of kinks before fracture. In recent years, aluminum alloys have been developed, which even in a soft state have strength characteristics that allow them to be used as a conductive material.

One of the promising areas for the use of aluminum is the electrical industry. Conducting aluminum alloys of the E-AlMgSi type (Aldrey) are representatives of this group of alloys. The paper presents the results of a study of the temperature dependence of heat capacity, heat transfer coefficient, and thermodynamic functions of an aluminum alloy E-AlMgSi (Aldrey) with bismuth. Research conducted in the "cooling" mode.

It was shown that the temperature capacity and the thermodynamic functions of the alloy E-AlMgSi (Aldrey) with bismuth increase with temperature, and the Gibbs energy decreases. Additives of bismuth up to 1 wt.% Reduce heat capacity, heat transfer coefficient, enthalpy and entropy of the initial alloy and increase the value of Gibbs energy.

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