The paper studies the processes of spontaneous polarization switching in PVDF and P(VDF-TrFE) polymer films produced by 4D printing. The samples were synthesized by the direct ink writing technology. It was found that polarization reversal in PVDF samples is not observed in alternating fields less than 70 MV/m, and in P(VDF-TrFE) samples – in fields less than 35 MV/m. This phenomenon is associated, firstly, with the large mass of the objects being repolarized, which is determined by the mass of the entire polymer chain, and, secondly, with a strong dipole-dipole interaction between adjacent polymer chains of the crystalline phase of the polymer. An increase in the electric field above the specified values leads to a sharp increase in the residual polarization values and the appearance of saturated dielectric hysteresis loops. The coercive field of the P(VDF-TrFE) copolymer films is two times smaller than the corresponding value for PVDF films (38 and 80 MV/m, respectively). At the same time, the residual polarization value for the copolymer films is slightly lower than for PVDF films (30 and 35 μC/m 2 , respectively). The hysteresis loops were modeled according to the Preisach model. This model is based on the assumption that all lamellar crystals in the polymer have the same spontaneous polarization, each crystal has its own value of the coercive field and a rectangular dielectric hysteresis loop. The simulation showed that the average coercive field of the lamellar crystals of the PVDF polymer film is 91 MV/m, and for the P(VDF-TrFE) copolymer sample – 46 MV/m. The dispersion characterizing the distributions of the coercive and internal fields has a value of 16 MV/m for the PVDF polymer and 14 MV/m for the P(VDF-TrFE) copolymer.

The paper presents the design features and technology of the formation of a low-pressure sensor, which is a heater deposited onto the surface of a porous aluminum-oxide membrane formed on aluminum foil. The structure is fully formed using inexpensive low temperature methods. It is shown that an increase in the porosity of the membrane region separating the heating element and the substrate makes it possible to effectively measure a pressure up to 2 × 10–2 Pa.

In this work, films of polyvinylidene fluoride, copolymer of vinylidene fluoride and trifluoroethylene have been studied. The samples were made by direct ink writing technology. Some of the produced films were polarized in the corona discharge field. The dependences of the relative permittivity on temperature were studied for the films. The study showed that for polyvinylidene fluoride films, no maximum is observed in the dependences of the permittivity on temperature, since the assumed temperature of the ferroelectric phase transition is higher than the melting temperature. The maximum in the temperature dependence of permittivity for polarized copolymer of vinylidene fluoride and trifluoroethylene films is shifted by 10 degrees C toward higher temperatures compared to the maximum for non-polarized films. In this case, the permittivity of non-polarized films has higher values compared to the corresponding value for polarized samples. This is due to an increase in the proportion of the beta-phase after polarization, as well as to the internal electric field caused by the space charge formed during the polarization process at the phase boundaries.

In this work, the polarization distribution over the volume of (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 crystals of the directions [001] and [111] was studied by the method of dynamic pyroelectric response. It is established that the value of the pyroelectric coefficient in the samples of both directions is the same. The domain structure of the studied crystals was visualized by piezoresponse force microscopy. It is shown that on the surface of the initial single crystals of these directions there is a small-sized labyrinth-like domain structure from 50 to 500 nm, characteristic of ferroelectric relaxors. At a depth of 50 microns from the crystal surface, a larger domain structure with a characteristic micron-scale domain size is observed. To determine the average thickness of a layer with an inhomogeneous polarization distribution, a theoretical model was used that analytically describes the possibilities of a dynamic pyroelectric method for studying the near-surface layer of ferroelectric materials. Theoretical calculations have shown that this method allows us to obtain accurate data on the thickness of the layer and its polarization state. It has been experimentally established that in a single crystal 0,955Pb(Zn1/3Nb2/3)O3-0,045PbTiO3 of the direction [001], the secondary pyroelectric effect contributes to the overall pyroelectric response much more than for the direction [111] due to the large value of the piezoelectric coefficient.

This paper describes manufacturing the film structures based on a polar copolymer of poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) using the process of drop-by-drop local deposition on metallized substrates. The produced samples were a crossbar structures of arrays of ferroelectric P(VDF-TrFE) microislands metallized with nickel stripes using a combined 2D printing method. For the polymer layer deposition, a number of solvents with different viscosities and dipole moments of molecules were considered, and their influence on the geometry and the polar properties of printed layers was shown. Using the piezoelectric force microscopy, the value of the piezoelectric modulus of d(33) at the nanoscale level was determined. This d(33) modulus is similar to values of d(33) for P(VDF-TrFE) films produced by the standard solvent cast method. On the base of amplitude of the pyroelectric current in the dynamic method, the value of the pyroelectric coefficient (p) was determined, varying from 2.10(-5) to 4.10(-5) C/(m(2)center dot K). These values are comparable to the pyroelectric coefficient of films P (VDF-TrFE) produced by the standard method. The highest values of d(33) and p correspond to structures produced from solutions containing more than 20% of propylene carbonate in the initial solvent, the molecules of which have a large (4,9 D) dipole moment.

This article reports a method to produce polymer films of polyvinylidene fluoride (PVDF) by an additive manufacturing (3D printing). Method Fused Deposition Modeling (FDM) allows using PVDF and its copolymers not only in microelectronics as pyroelectric and piezoelectric sensors, as well as creating dynamic memory elements, organic solar cells and used in robotics. The surface morphology of the samples observed by scanning electron microscopy (SEM) presents in this paper. Pyroelectric measurements performed by the dynamic method show the presence of a noticeable pyroelectric response in PVDF films obtained using additive technologies, bypassing the orientation extraction stage. The calculation of the pyroelectric coefficient gives values corresponding to the values of the pyroelectric coefficient for PVDF samples obtained by traditional methods.

In this work, the electrophysical properties of metal-ferroelectric-semiconductor structures – Cu/LiNbO₃/Si and Ag/LiTaO₃/Si – with a ferroelectric layer thickness of 200 nm have been studied. The ferroelectric layers were deposited by RF‐magnetron sputtering. A topography study of thin film surface revealed a grain structure. The electrical conductivity mechanisms in Cu/LiNbO₃/Si and Ag/LiTaO₃/Si were considered. In a dependence of bias voltage value, there are a space charge-limited current, hopping conduction, and Schottky emission in Cu/LiNbO₃/Si structures. For Ag/LiTaO₃/Si structures, the space charge-limited current and hopping conduction were observed. An asymmetry of the current-voltage characteristics may indicate the presence of a potential barrier at the interface. For the studied structures, the value of the potential barrier was determined.

In this work, composite films of a copolymer of vinylidene fluoride with trifluoroethylene P(VDF-TrFE) comprising microcrystals of deuterated triglycine sulfate (DTGS) were produced. The pyroelectric properties of the composite samples were studied by the dynamic method. Pyroelectric measurements indicated an extreme dependence of the pyroelectric coefficient on the concentration of DTGS inclusions in the composite. Piezoelectric modules were macroscopically measured in static mode. The measured piezoelectric moduli d (31) and d (33) show ambiguous dependences on the volume fraction of DTGS inclusions.

In this work, the electrophysical properties of metal-ferroelectric-semiconductor structures --- Cu/LiNbO3/Si and Ag/LiTaO3/Si --- with a ferroelectric layer thickness of 200 nm have been studied. The ferroelectric layers were deposited by RF magnetron sputtering. A topography study of thin film surface revealed a grain structure. The electrical conductivity mechanisms in Cu/LiNbO3/Si and Ag/LiTaO3/Si were considered. In a dependence of bias voltage value, there are a space charge-limited current, hopping conduction, and Schottky emission in Cu/LiNbO3/Si structures. For Ag/LiTaO3/Si structures, the space charge-limited current and hopping conduction were observed. An asymmetry of the current-voltage characteristics may indicate the presence of a potential barrier at the interface. For the studied structures, the value of the potential barrier was determined Keywords: metal-ferroelectric-semiconductor structures, thin films, lithium niobate, lithium tantalate, electrophysical properties, electrical conductivity, potential barrier.

In this work, we carried out a comparative study of the surface structure of barium-strontium titanate Ba1-xSrxTiO3 ceramics of various compositions (x = 0,1; 0,2; 0,25; 0,3; 0,4 and 0,5) and the dielectric characteristics of samples in a wide temperature range. It has been found that with increasing the strontium content, a decrease in the density of ceramic samples is observed. An increase in the strontium concentration in the composition of the ceramics under study leads to a reduction in the average grain size by an order of magnitude, and fine grains from 2 mu m to 200 nm. For all ceramic samples of barium-strontium titanate, there is a deviation of the elemental composition from the stoichiometric at the nanoscale. The closest to the stoichiometric composition in terms of the molar content of elements is the composition of the Ba0,75Sr0,25TiO3 samples. It was found that the samples of this composition have the highest value of the permittivity at room temperature. Temperature studies of the dielectric permittivity showed the existence of two maxima: at a temperature of 130 degrees C, corresponding to the Curie temperature of pure barium titanate ceramics, and at lower temperatures in the range from 10 to 100 degrees C, the second depends on the strontium content. The low-temperature maximum for the epsilon value corresponds to the diffuse transition of the solid solution Ba1-xSrxTiO3, whose relaxor properties are confirmed by deviation of the temperature dependence from the Curie-Weiss law. The samples of Ba0,75Sr0,25TiO3 composition have the most pronounced relaxor behavior.

This work is devoted to the technological features of creating an array of pyroelectric nanoparticles placed in the pores of a silicon oxide membrane, ensuring their thermal insulation both from each other and from the supporting substrate. Mechanisms of anodic oxidation of the Al/Ti/SiO2 structure, ensuring the self-organization of a nanostructured oxide mask with specified geometric parameters, have been established. It has been shown that from a certain thickness of the adhesion layer, overgrowing of the open areas of the mask with titanium oxide nanoparticles does not occur. The regularities of the method of local ion etching of multilayer structures are determined, which ensures control of the depth of the formed pores by controlling the ion current. A correlation has been established between the lateral size of the cavities in silicon and the aspect ratio of aluminum oxide pores. The possibility of forming a silicon oxide membrane with pyroelectric polymer nanoparticles embedded in its pores has been demonstrated.

В работе проведены исследования пироэлектрической активности наноразмерных тонких поликристаллических пленок ниобата лития, изготовленных методом высокочастотного магнетронного распыления и методом лазерной абляции, а также тонких поликристаллических пленок танталата лития, изготовленных методом высокочастотного магнетронного распыления. С использованием динамического метода исследования пироэлектрического эффекта выяснено, что все образцы обладают самопроизвольной поляризацией, возникающей во время постростового термического отжига. Оценка пироэлектрического коэффициента показала, что значения пирокоэффициента тонких пленок ниобата лития и танталата лития в несколько раз меньше значений пирокоэффициента для объемных кристаллов соответствующих материалов. Это может быть связано с тем, что вектор поляризации части зерен лежит в плоскости пленки, а также с существующими в объеме пленки и на границе раздела пленка/подложка ловушками, на которых носители заряда рекомбинируют и не участвуют в генерации пироэлектрического тока. In this work, we studied the pyroelectric activity of thin polycrystalline lithium niobate films fabricated by radio frequency magnetron sputtering and laser ablation, and thin polycrystalline lithium tantalate films fabricated by radio frequency magnetron sputtering. Using the dynamic method of studying the pyroelectric effect, it was found that all samples have self-polarization that occurs during the post-growth thermal annealing of the structure. An estimate of the pyroelectric coefficient showed that the values of the pyroelectric coefficient of lithium niobate and lithium tantalate thin films are several times lower than the values of the pyroelectric coefficient for bulk crystals of the corresponding materials. This may be due to the fact that the polarization vector of some grains lies in the film plane, as well as to the traps existing in the film volume and at the film/substrate interface, on which charge carriers recombine and do not participate in the generation of the pyroelectric current.

In this work, on the base of piezoelectric and pyroelectric measurements, it was shown that the calcium orthovanadate crystals pure and doped exhibit a natural unipolar state. Doping these crystals with manganese and thulium ions did not affect the magnitude and behavior of dielectric permittivity. However, the presence of doping ions led to reducing the local piezoelectric response and stabilizing the unipolar state.