Microstructure and Properties of PZT Films with Different PbO Content-Ionic Mechanism of Built-In Fields Formation

Low-Pb High-Piezoelectric Ceramic System (1−x)Ba(Zr0.18Ti0.82)O3–x(Ba0.78Pb0.22)TiO3

Piezoelectric materials, especially Pb-based piezoelectric materials, are widely used in the key components of sensors, actuators, and transducers. Due to the rising concern of the toxicity of Pb, global legislation has been adopted to restrict the use of Pb. Given that the available Pb-free piezoelectric materials cannot replace the Pb-based ones for various reasons, we designed and fabricated a low-Pb piezoelectric solid-solution ceramic system, (1–x)Ba(Zr_0.18Ti_0.82)O₃–x(Ba_0.78Pb_0.22)TiO₃ (denoted as BZ_0.18T–xBP_0.22T herein). The crystal structure, ferroelectric, dielectric, and piezoelectric properties of the BZ_0.18T–xBP_0.22T system were systematically studied. With the increase in BP_0.22T content, the structure of the samples changed from a rhombohedral phase to a tetragonal phase; the intermediate composition x = 0.5 was located at the morphotropic phase boundary of the system and corresponded to the state with the coexistence of the rhombohedral and tetragonal phases. Moreover, x = 0.5 exhibited the optimum comprehensive properties among all the samples, with a piezoelectric coefficient d₃₃ of 240 pC/N, a maximum dielectric temperature Tm of 121.1°C, and a maximum polarization Pm of 15 μC/cm². Our work verifies the validity of the route to design low-Pb high-piezoelectric materials and may stimulate the interests for exploring new low-Pb high-performance ferroelectric and piezoelectric materials.

Creation of a Nanomodified Backfill Based on the Waste from Enrichment of Water-Soluble Ores

The paper analyzes losses during the development of low-value water-soluble ore deposits. The importance of development systems with backfill is shown. The use of industrial wastes of water-soluble ores to replace specially produced inert components in the preparation of backfill seems to be a good way to utilize them. The aim of the work was to create a fill mass with improved strength properties based on industrial wastes of water-soluble ores activated with a nanomodifying material. The characteristics (chemical and granulometric compositions) of an aggregate of the backfill based on the waste from enrichment of water-soluble ores are given. The validation of the hardening mixture compositions for various mining systems was carried out considering: the specified strength, the time of the artificial mass erection, the time to achieve the required strength properties of the material, which determine the possible intensity of the mining operations; method of transporting the backfill. The expediency of using a multilayer fulleroid nanomodifier astralene as a nanomodifying additive has been proved. The effect of the backfill activation with a nanomodifying additive, astralene, on the structural changes of halite wastes from the halurgic enrichment of water-soluble ores (potash) was investigated. To study the strength properties of the fill mass, the comparative analytical method was used. The strength properties of the backfill were measured in standard test periods, taking into account the intensity of hardening of the backfill material (after 7, 14, 28, 60, 90 days). To obtain reliable results, 10 backfill samples were tested at each of the scheduled dates. The shape and chemical composition of crystalline new forms were studied. Studies were performed using X-ray phase analysis and scanning electron microscopy. As a result of uniaxial compression of hardening backfill samples, the dependence of the ultimate strength on the astralene content and the hardening time were established. It has been experimentally proved that the use of a nanomodifying additive, astralene, in the backfill allows an increase in the strength properties of the created artificial mass by 1.76–2.36 times while reducing binder consumption.

Composite Ferroelectric Coatings Based on a Heat-Resistant Polybenzoxazole Polymer Matrix

The polycondensation of 5,5-methylene bis(2-aminophenol) and the mixture of diamines 5,5-methylene bis(2-aminophenol) and 4,4-(hexafluoroisopropylidene)dianiline (molar ratio 0.8:0.2) with isophthaloyl dichloride was used to synthesize a new heat resistant binder of the composites for microelectronics: poly(o-hydroxyamide) (POA) and poly(amido-o-hydroxy amide) (POA-F). The thermal stability of synthesized polymer coatings, as well as based on them photosensitive compositions with a naphthoquinondiazide photosensitive component were studied in the temperature range from 100 to 500 °C. Ferroelectric composites with nanodispersed lead titanate zirconate powder filler were formed based on these polymer matrices. By manipulating the conditions of the polymer formation, we obtained matrices with different stiffnesses, which reflected on the properties of the composite. The electrophysical parameters of the synthesized polymer and ferroelectric composite coatings were measured in the frequency range from 0.1 Hz to 1.5 GHz and the temperature range from 0 to 300 °C. The frequency and temperature stability of the dielectric constant of ferroelectric composite coatings up to 10 MHz and 300 °C, respectively, are noted. The influence of the composition and structure of the polymer matrix and the grain/matrix interfaces on the thermal stability of the dielectric parameters of composite films is estimated. The shift of the phase transition region toward higher temperatures in the composite structure, as well as the sufficient rigidity of the poly(benzoxazole) matrix, provide high temperature and frequency stability of the dielectric constant of the studied composites.