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The possibility observation of the electric field controlled multicaloric response through quasi-isostatic compression as a result of the converse piezoelectric effect was demonstrated on the cylindrical type magnetoelectric composite MnAs/PZT. It was shown that an electric voltage of 100 V corresponding to an electric field of E ∼0.3 kV/mm applied to the walls of the piezoelectric component PZT of the MnAs/PZT composite contributes to an increase in the maximum adiabatic temperature change by 0.2 K in the temperature range of the magnetostructural phase transition of MnAs ∼317 K at a magnetic field change of 1.8 T. Numerical analysis using the finite element method has shown that an electric field voltage of 100 V is capable of creating a quasi-isostatic mechanical stress in the region inside a cylindrical PZT tube of ∼3 MPa. Moreover, in the region of weak pressures up to 10 MPa, the contribution to the total adiabatic temperature change from piezo-mechanical compression linearly depends on the electrical voltage that can be used for control by magnetic and caloric properties of multicaloric materials. [ABSTRACT FROM AUTHOR]

Using commercially available components, a compact laboratory-type prototype has been developed and assembled to demonstrate single and multicaloric effects arising from single and cyclic applications of magnetic fields and uniaxial mechanical loads. Using the example of the LaFe11.4Mn0.3Si1.3H1.6 alloy with a first-order phase transition near room temperature, the possibility of observing magnetocaloric, elastocaloric, and multicaloric effects is demonstrated. It is shown that by selecting protocols for applying combined external influences: magnetic field and mechanical load, it is possible to observe a synergistic effect for adiabatic temperature change, which amounts to 1.17 K (0.31 T and 19 MPa) at a temperature of 291.5 K for the multicaloric effect, which exceeds the corresponding value of |ΔT| = 0.75 K (0.31 T) at a temperature of 291.65 K for the magnetocaloric effect. The proposed approaches and obtained results can be used for the development of new prototypes of multicaloric cooling systems and the optimization of current ones. [ABSTRACT FROM AUTHOR]

β-tricalcium phosphate (β-TCP) is a promising material in regenerative traumatology for the creation of bone implants. Previously, it was established that doping the structure with certain cations can reduce the growth of bacterial activity. Recently, much attention has been paid to co-doped β-TCP, that is explained by their ability, on the one hand, to reduce cytotoxicity for cells of the human organism, on the other hand, to achieve a successful antibacterial effect. Sr, Cu-co-doped solid solutions of the composition Ca9.5–xSrxCu(PO4)7 was obtained by the method of solid-phase reactions. The Rietveld method of structural refinement revealed the presence of Sr2+ ions in four crystal sites: M1, M2, M3, and M4. The M5 site is completely occupied by Cu2+. Isomorphic substitution of Ca2+ → (Sr2+and Cu2+) expands the concentration limits of the existence of the solid solution with the β-TCP structure. No additional phases were formed up to x = 4.5 in Ca9.5–xSrxCu(PO4)7. Biocompatibility tests were performed on cell lines of human bone marrow mesenchymal stromal cells (hMSC), human fibroblasts (MRC-5) and osteoblasts (U-2OS). It was demonstrated that cytotoxicity exhibited a concentration dependence, along with an increase in osteogenesis and cell proliferation. Ca9.5–xSrxCu(PO4)7 powders showed significant inhibitory activity against pathogenic strains Escherichia coli and Staphylococcus aureus. Piezoelectric properties of Ca9.5–xSrxCu(PO4)7 were investigated. Possible ways to achieve high piezoelectric response are discussed. The combination of bioactive properties of Ca9.5–xSrxCu(PO4)7 renders them multifunctional materials suitable for bone substitutes. [ABSTRACT FROM AUTHOR]

The new xMnAs/(1 − x)PMN–PT (x = 0.2, 0.3) multicaloric composites, consisting of the modified PMN–PT-based relaxor-type ferroelectric ceramics and ferromagnetic compound of MnAs were fabricated, and their structure, magnetic, dielectric properties, and caloric effects were studied. Both components of the multicaloric composite have phase transition temperatures around 315 K, and large electrocaloric (~0.27 K at 20 kV/cm) and magnetocaloric (~13 K at 5 T) effects around this temperature were observed. As expected, composite samples exhibit a decrease in magnetocaloric effect (<1.4 K at 4 T) in comparison with an initial MnAs magnetic component (6.7 K at 4 T), but some interesting phenomena associated with magnetoelectric interaction between ferromagnetic and ferroelectric components were observed. Thus, a composite with x = 0.2 exhibits a double maximum in isothermal magnetic entropy changes, while a composite with x = 0.3 demonstrates behavior more similar to MnAs. Based on the results of experiments, the model of the multicaloric effect in an MnAs/PMN–PT composite was developed and different scenario observations of multicaloric response were modeled. In the framework of the proposed model, it was shown that boosting of caloric effect could be achieved by (1) compilation of ferromagnetic and ferroelectric components with large caloric effects in selected mass ratio and phase transition temperature; and (2) choosing of magnetic and electric field coapplying protocol. The 0.3MnAs/0.7PMN–PT composite was concluded to be the optimal multicaloric composite and a phase shift ∆φ = −π/4 between applied manetic fields can provide a synergetic caloric effect at a working point of 316 K. [ABSTRACT FROM AUTHOR]

The creation of multi-stimuli-sensitive composite polymer–inorganic materials is a practical scientific task. The combination of photoactive magneto-piezoelectric nanomaterials and ferroelectric polymers offers new properties that can help solve environmental and energy problems. Using the doctor blade casting method with the thermally induced phase separation (TIPS) technique, we synthesized a hybrid polymer–inorganic nanocomposite porous membrane based on polyvinylidene fluoride (PVDF) and bismuth ferrite (BiFeO3/BFO). We studied the samples using transmission and scanning electron microscopy (TEM/SEM), infrared Fourier spectroscopy (FTIR), total transmission and diffuse reflection, fluorescence microscopy, photoluminescence (PL), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vibrating-sample magnetometer (VSM), and piezopotential measurements. Our results demonstrate that the addition of BFO increases the proportion of the polar phase from 76.2% to 93.8% due to surface ion–dipole interaction. We also found that the sample exhibits laser-induced fluorescence, with maxima at 475 and 665 nm depending on the presence of nanoparticles in the polymer matrix. Furthermore, our piezo-photocatalytic experiments showed that under the combined actions of ultrasonic treatment and UV–visible light irradiation, the reaction rate increased by factors of 68, 13, 4.2, and 1.6 compared to sonolysis, photolysis, piezocatalysis, and photocatalysis, respectively. This behavior is explained by the piezoelectric potential and the narrowing of the band gap of the composite due to the mechanical stress caused by ultrasound. [ABSTRACT FROM AUTHOR]

The effect of a high magnetic field up to 12 T and a high hydrostatic pressure up to 12 kbar on the stability of the metamagnetic isostructural phase transition and the multicaloric effect of Fe49Rh51 alloy has been studied. The phase transition temperature shifts under the magnetic field and the hydrostatic pressure on with the rates of dTm/μ0dH = −9.2 K/T and dTm/dP = 3.4 K/kbar, respectively. The magnetocaloric and multicaloric (under two external fields) effects were studied via indirect method using Maxwell relations. The maximum of the entropy change is increasing toward the high temperature region from ∆S~2.5 J/(kg K) at 305 K to ∆S~2.7 J/(kg K) at 344 K under simultaneously applied magnetic field of 0.97 T and hydrostatic pressure of 12 kbar. The obtained results were explained using the first-principle calculations of Gibbs energies and the phonon spectra of the ferromagnetic and the antiferromagnetic phases. Taking into account the low concentration of antisite defects in the calculation cells allows us to reproduce the experimental dTm/dP coefficient. [ABSTRACT FROM AUTHOR]

Nowadays, magnetoelectric nanomaterials are on their way to finding wide applications in biomedicine for various cancer and neurological disease treatment, which is mainly restricted by their relatively high toxicity and complex synthesis. This study for the first time reports novel magnetoelectric nanocomposites of CoxFe3−xO4-BaTiO3 series with tuned magnetic phase structures, which were synthesized via a two-step chemical approach in polyol media. The magnetic CoxFe3−xO4 phases with x = 0.0, 0.5, and 1.0 were obtained by thermal decomposition in triethylene glycol media. The magnetoelectric nanocomposites were synthesized by the decomposition of barium titanate precursors in the presence of a magnetic phase under solvothermal conditions and subsequent annealing at 700 °C. X-ray diffraction revealed the presence of both spinel and perovskite phases after annealing with average crystallite sizes in the range of 9.0–14.5 nm. Transmission electron microscopy data showed two-phase composite nanostructures consisting of ferrites and barium titanate. The presence of interfacial connections between magnetic and ferroelectric phases was confirmed by high-resolution transmission electron microscopy. Magnetization data showed expected ferrimagnetic behavior and σs decrease after the nanocomposite formation. Magnetoelectric coefficient measurements after the annealing showed non-linear change with a maximum of 89 mV/cm*Oe with x = 0.5, 74 mV/cm*Oe with x = 0, and a minimum of 50 mV/cm*Oe with x = 0.0 core composition, that corresponds with the coercive force of the nanocomposites: 240 Oe, 89 Oe and 36 Oe, respectively. The obtained nanocomposites show low toxicity in the whole studied concentration range of 25–400 μg/mL on CT-26 cancer cells. The synthesized nanocomposites show low cytotoxicity and high magnetoelectric effects, therefore they can find wide applications in biomedicine. [ABSTRACT FROM AUTHOR]

Direct and indirect measurements of the magnetocaloric effect in La0.7Pb0.3-xBaxMnO3 (x = 0.05, 0.10, and 0.15) manganite were reported. The effect of Pb substitution with Ba on the structural, magnetic, and magnetocaloric properties of these compounds was investigated. The X-ray analysis reveals a structural transition upon doping. The rhombohedral structure of x = 0.05 is transformed into a mixture of cubic and rhombohedral phases for both samples x = 0.10 and x = 0.15. For all the samples, magnetic versus temperature analysis shows a transition from a paramagnetic (PM) to a ferromagnetic state (FM). The zero-field heat capacity measurement was also performed. The magnetocaloric efficiency was determined from adiabatic temperature and isothermal magnetization curves using Maxwell relation. It is found that the sample with the composition x = 0.10 exhibits the highest value of ΔTad and ΔSm which were found to be 1.75 K and 1.445 Jkg−1 K−1 at 3 T respectively. The corresponding relative cooling power (RCP) was around 145.5 Jkg−1. The phenomenological construction of the universal curves and the Banerjee criterion revealed a second-order phase transition for all samples. [ABSTRACT FROM AUTHOR]

Polymer-based multiferroics, combining magnetic and piezoelectric properties, are studied experimentally—from synthesis to multi-parameter characterization—in view of their prospects for fabricating biocompatible scaffolds. The main advantage of these systems is facile generation of mechanical deformations and electric signals in response to external magnetic fields. Herein, we address the composites based on PVDF-TrFE polymer matrices filled with a combination of piezoelectric (BaTiO3, BTO) and/or ferrimagnetic (Zn0.25Co0.75Fe2O4, ZCFO) particles. It is shown that the presence of BTO micron-size particles favors stripe-type structuring of the ZCFO filler and enhances the magnetoelectric response of the sample up to 18.6 mV/(cm∙Oe). Besides that, the admixing of BTO particles is crucial because the mechanical properties of the composite filled with only ZCFO is much less efficient in transforming magnetic excitations into the mechanical and electric responses. Attention is focused on the local surfacial mechanical properties since those, to a great extent, determine the fate of stem cells cultivated on these surfaces. The nano-indentation tests are accomplished with the aid of scanning probe microscopy technique. With their proven suitable mechanical properties, a high level of magnetoelectric conversion and also biocompatibility, the composites of the considered type are enticing as the materials for multiferroic-based polymer scaffolds. [ABSTRACT FROM AUTHOR]

The paper investigates the magnetobarocaloric effect in a multiferroic composite made of ferroelectric and manganite components. Such a phenomenon can be classified as a secondary multicaloric effect. Its theoretical description is provided. In the presence of a magnetic field a temperature-dependent elastic field arises in the magnetostrictive material that results in the magnetobarocaloric effect. The effect reaches its maximum entropy change of 0.044 J kg−1K–1 at 312.5 K for the composite under study. [ABSTRACT FROM AUTHOR]

This work is devoted to study the peculiarities of charge transfer in SiO2(Ni)/Si nanosystems formed as a result of the electrochemical deposition of nickel into the pores of the ion-track silicon oxide template on silicon. Special attention is given to analysis of the results in the context of the band structure and physical properties of dielectric on semiconductor systems with metallic inclusions in the dielectric matrix. Experimental studies of the current-voltage characteristics of SiO2(Ni)/Si nanostructures demonstrated that value of potential barrier on the Si/metal interface in the pores of the silicon oxide template depended on temperature. On the basis of these results an interpretation of the charge transfer mechanisms in SiO2(Ni)/Si nanosystems at different temperature ranges was proposed. In the temperature region of ~300–200 K charge carrier motion occurs through the n-Si with an employment of metallic clusters in pores being in a contact with the semiconductor, by means of the overbarrier emission of electrons from higher energy levels of Si conduction band. In the lower temperatures (~200-100 K) a current flow takes place only through the semiconductor due to an increase of resistivity on energy barriers n-Si/metal, which leads to a practically complete exclusion of a participation of the metal in the charge transport process. In the low temperatures (~100–20 K), the variable range hopping conduction between pores on the SiO2/Si boundary, containing localized states, dominates. [ABSTRACT FROM AUTHOR]

The paper is concerned with the structure and functional properties of bismuth ferrite–barium titanate, 0.75BiFeO3–0.25BaTiO3, solid solutions. Such materials are attracting attention due to their potential applications in high temperature piezoelectric transducers for use in demanding environments in process monitoring, for example. The article focuses on the mechanism of incorporation of the minor dopant lanthanum oxide, either in the form of isovalent or donor-type substitution. It is shown that the development of chemical heterogeneity in the form of core–shell grain microstructures, linked to donor-type substitution, plays a key role in controlling the functional behaviour. The use of an air-quenching procedure results in dramatic improvements in the ferroelectric properties, accompanied by a transformation of the shell regions from a pseudo-cubic, Pm3̅m, to rhombohedral, R3c, structure. These observations are interpreted in terms of a novel mechanism involving nanoscale phase separation in the ‘shell’ regions during slow cooling, which impedes the development of ferroelectric ordering and leads to the formation of a nano-polar relaxor ferroelectric state. The work highlights the importance of immiscibility in bismuth-based ferroelectric perovskite solid solutions and illustrates how their ferroelectric, piezoelectric, dielectric energy storage, ferromagnetic and magneto-electric properties can be tuned by consideration of the substitution mechanism and control of thermal processing parameters. [ABSTRACT FROM AUTHOR]

We report the results of studies of the magnetic and transport properties of Fe49Rh51 alloy prepared by different sequences of quenching and the annealing process. The temperature dependences of the relative initial magnetic permeability and resistivity are analyzed. An optimal regime consisting of annealing at 1300 K for 440 min and quenching from 1300 K to 275 K is found to observe the desired narrow antiferromagnetic–ferromagnetic transition in Fe49Rh51 alloy under cyclic conditions. This has the potential to increase the efficiency of cooling devices based on the magnetocaloric effect of magnetic materials with a first-order field-induced phase transition. [ABSTRACT FROM AUTHOR]

The possibility of the formation of high entropy single-phase perovskites using solid-state sintering was investigated. The BaO–SrO–CaO–MgO–PbO–TiO2, BaO–SrO–CaO–MgO–PbO–Fe2O3 and Na2O–K2O–CaO–La2O3–Ce2O3–TiO2 oxide systems were investigated. The optimal synthesis temperature is found between 1150 and 1400 °C, at which the microcrystalline single phase with perovskite structure was produced. The morphology, chemical composition, crystal parameters and dielectric properties were studied and compared with that of pure BaTiO3. According to the EDX data, the single-phase product has a formula of Na0.30K0.07Ca0.24La0.18Ce0.21TiO3 and a cubic structure. [ABSTRACT FROM AUTHOR]

Multiferroic BiFe1−xZnxO3 ceramics were prepared by solution combustion method. Their structure, magnetoelectric, dielectric, magnetic, thermal characteristics were studied. The magnetic M(T) and heat capacity Cp(T) measurements demonstrate an antiferromagnetic to paramagnetic phase transition (TN) around 635 K. The anomaly on the temperature dependence of the dielectric constant near TN was observed, which could be induced by the magnetoelectric coupling between electric and magnetic ordering. The magnetoelectric behavior was also confirmed by the linear relation between Δε and M2, which is in the agreement of the Ginzburg-Landau theory for the second-order phase transition. [ABSTRACT FROM AUTHOR]