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The effect of the size of Bi2Fe4O9 and BiFeO3 nanoparticles on the magnetoelectric interaction in the Bi2Fe4O9/BiFeO3 composite with a percentage ratio of 67/33 has been studied. The electrostriction and electric polarization on electric and magnetic field in wide temperature range has been measured. The hysteresis of the polarization and I‒V characteristics has been found. Temperature ranges with activation and hopping types of conductivity have been found. The mechanism of electric polarization and the crossover temperature from dipole polarization to migration polarization at 260 K have been established. Linear and quadratic contributions to the magnetoelectric effect have been found. Below 120 K the linear contribution is an order of magnitude greater than the quadratic contribution and above 240 K the quadratic contribution to the ME effect prevails. Models have been proposed to explain the enhancement of the magnetoelectric effect as a result of the migration polarization in mullite and linear magnetoelectric effect in bismuth ferrite. The correlation of temperatures of the extremum of the temperature coefficient of the electrical resistance and the magnetic phase transition in mullite at 260 K indicates a polaron-type conductivity and a strong electron‒phonon interaction. A change in the sign of the electrostriction coefficient upon heating and the compression temperature of the composite in an electric field was found.Graphical Abstract: The effect of the size of Bi2Fe4O9 and BiFeO3 nanoparticles on the magnetoelectric interaction in the Bi2Fe4O9/BiFeO3 composite with a percentage ratio of 67/33 has been studied. The electrostriction and electric polarization on electric and magnetic field in wide temperature range has been measured. The hysteresis of the polarization and I‒V characteristics has been found. Temperature ranges with activation and hopping types of conductivity have been found. The mechanism of electric polarization and the crossover temperature from dipole polarization to migration polarization at 260 K have been established. Linear and quadratic contributions to the magnetoelectric effect have been found. Below 120 K the linear contribution is an order of magnitude greater than the quadratic contribution and above 240 K the quadratic contribution to the ME effect prevails. Models have been proposed to explain the enhancement of the magnetoelectric effect as a result of the migration polarization in mullite and linear magnetoelectric effect in bismuth ferrite. The correlation of temperatures of the extremum of the temperature coefficient of the electrical resistance and the magnetic phase transition in mullite at 260 K indicates a polaron-type conductivity and a strong electron‒phonon interaction. A change in the sign of the electrostriction coefficient upon heating and the compression temperature of the composite in an electric field was found. [ABSTRACT FROM AUTHOR]

Improvement of physical and mechanical characteristics of mineral-filled polyethylene (MFPE) upon addition of alumina nanofibers with a high aspect ratio has been experimental studied. It is shown that, at the weight concentration of alumina nanofibers of 0.1 wt %, the ultimate tensile strength increases from 3.82 ± 0.04 to 6.70 ± 0.07 MPa and the Young's modulus increases from 1.08 ± 0.01 to 1.38 ± 0.01GPa (with respect to MFPE). The MFPE/Al2O3 nanofiber composite can be described within a model of weak adhesive interaction between a filler and a matrix with high friction. [ABSTRACT FROM AUTHOR]

The Eu3+-doped red-orange emitting phosphor of tellurite glass 0.25Li2O-0.20Y2O3-0.5TeO2-0.05Eu2O3 has been synthesized by the melt quenching method. The amorphous nature of the glass has been verified by XRD measurements. The photoluminescence excitation and emission spectra, the luminescence decay curves have been investigated for the composition. The phosphor can be efficiently excited by the near UV light to realize the intense narrow red emission line (611 nm) corresponding to forced electric dipole transition 5D0 → 7F2 of Eu3+ ions. The Li2O-Y2O3-TeO2:Eu3+glass phosphor is a potential red-orange emitting candidate for the application in WLEDs. [ABSTRACT FROM AUTHOR]

Single crystals of Cs2NaBi(MoO4)3 are grown by annealing (673-773 K, 60 h) of a mixture of Na2MoO4 (obtained via calcination of the hydrate), Cs2MoO4 (obtained by annealing Cs2CO3 and MoO3, 823 K, 60 h), and Bi2(MoO4)3 (obtained by reacting Bi2O3 and MoO3, 723-773 K, 50 h). [ABSTRACT FROM AUTHOR]

In this Letter, we consider optical bound states in the continuum (BICs) in the infrared range supported by an all-dielectric metasurface in the form of subwavelength dielectric grating. We apply the random forest machine learning method to predict the frequency of the BICs as dependent on the optical and geometric parameters of the metasurface. It is found that the machine learning approach outperforms the standard least square method at the size of the dataset of ≈4000 specimens. It is shown that the random forest approach can be applied for predicting the subband in the infrared spectrum into which the BIC falls. The important feature parameters that affect the BIC wavelength are identified.

Single crystals of SmAl 3 (BO 3 ) 4 were synthesized by the group growth on seeds method. The crystal structure was solved using a single-crystal experiment and the purity of the bulk material was proved by the Rietveld method. This borate crystallizes in the monoclinic C2/c space group with unit-cell parameters a = 7.2386 (3), b = 9.3412 (5), c = 11.1013 (4) Å and β = 103.2240 (10)°. IR and Raman spectroscopic analyses confirmed the monoclinic structure of SmAl 3 (BO 3 ) 4 . Under 532.1 nm excitation, luminescence spectra exhibit bands assignable to the transitions from 4 G 5/2 to 6 H 5/2 , 6 H 7/2 , 6 H 9/2 and 6 H 11/2 . The similarity of the luminescence spectra of the trigonal and monoclinic polymorphs is explained by the minor role of Sm-O bond distortion and the primary role of rotational distortion of SmO 6 octahedra. The smaller covalency of the Sm-O bond in alumoborates is deduced in comparison with galloborates. Calorimetric measurements did not reveal high-temperature structural phase transitions up to a temperature of 720 K.

The oxidation process of samariumoxysulfide was studied in the temperature range of 500-1000 °C. Our DTA investigation allowed for establishing the main thermodynamic (∆Hº exp = -654.6 kJ/mol) and kinetic characteristics of the process (E a = 244 kJ/mol, A = 2 × 10 10 ). The enthalpy value of samarium oxysulfate (ΔHºf (Sm 2 O 2 SO 4(monocl) ) = -2294.0 kJ/mol) formation was calculated. The calculated process enthalpy value coincides with the value determined in the experiment. It was established that samarium oxysulfate crystallizes in the monoclinic symmetry class and its crystal structure belongs to space group C2/ c with unit cell parameters a = 13.7442 (2), b = 4.20178 (4) and c = 8.16711 (8)Å, β = 107.224 (1)°, V = 450.498 (9)Å 3 , Z = 4. The main elements of the crystalline structure are obtained and the cation coordination environment is analyzed in detail. Vibrational spectroscopy methods confirmed the structural model adequacy. The Sm 2 O 2 SO 4 luminescence spectra exhibit three main bands easily assignable to the transitions from 4 G 5/2 state to 6 H 5/2 , 6 H 7/2 , and 6 H 9/2 multiplets.

Microcrystals of orthorhombic rubidium samarium molybdate, β-RbSm(MoO4)2, have been fabricated by solid state synthesis at T = 450 °C, 70 h, and at T = 600 °C, 150 h. The crystal structure has been refined by the Rietveld method in space group Pbcn with cell parameters a = 5.0984(2), b = 18.9742(6) and c = 8.0449(3) Å (R(B) = 1.72%). Thermal properties of β-RbSm(MoO4)2 were traced by DSC over the temperature range of T = 20-965 °C, and the earlier reported β ↔ α phase transition at T ∼ 860-910 °C was not verified. The electronic structure of β-RbSm(MoO4)2 was studied by employing theoretical calculations and X-ray photoelectron spectroscopy. It has been established that the O 2p-like states contribute mainly to the upper part of the valence band and occupy the valence band maximum, whereas the Mo 4d-like states contribute mainly to the lower part of the valence band. Chemical bonding effects have been analysed from the element core level binding energy data. In addition, it was found that the luminescence spectrum of β-RbSm(MoO4)2 is rather peculiar among the Sm(3+) containing materials. The optical refractive index dispersion in β-RbSm(MoO4)2 was also predicted by the first-principles calculations.

Mn2GeO4 single crystals with the olivine structure grown by the modified flux method have been investigated. Pronounced magnetic phase transitions at T1 = 47.7 K, T2 = 17 K and T3 = 5.5 K, with T2 being dependent on an applied magnetic field, have been found. Based on the data of magnetic, resonance and temperature measurements, the entire phase diagram of Mn2GeO4 has been built. Mn2GeO4 is shown to be a material with a complex magnetic structure consisting of two magnetic subsystems.