In our study, we present comprehensive findings on the structural properties of Pr2Ti2O7 2 Ti 2 O 7 across a broad pressure range of 0-30 GPa. Neutron diffraction experiments, conducted under ambient conditions, offer crucial structural insights into the initial monoclinic phase with the P21 1 space group. As pressure increased, a significant phase transition to the monoclinic P21/m 1 /m phase occurred at 13.8 GPa. Structural data analysis from X-ray diffraction highlights the essence of this transition, identifying it as the tilting of Ti-O6 6 octahedra. High-pressure Raman spectroscopy data unequivocally confirms the phase transition, detecting anomalies in the baric dependencies of some vibration modes of Pr2Ti2O7 2 Ti 2 O 7 and the emergence of new modes in the Raman spectra within the pressure region associated with the phase transition. The analysis of these novel vibration modes points to alterations in the Ti-O6 6 octahedra, emphasizing the pivotal role played by Ti4+ 4 + and O2 2- ions in the mechanism of the pressure- driven phase transition.

The crystal structure and vibrational spectra of cation-deficient nanostructured zinc ferrite Zn0.34Fe2.53 square O-0.13(4) (where square denotes the cation vacancies) have been studied using X-ray diffraction and Raman spectroscopy methods in the pressure range of 0-34 GPa. Our results indicate a phase transition from the initial cubic phase with space group Fd 3 m to a high-pressure phase with orthorhombic symmetry of Bbmm at pressures above 18 GPa. This phase transition is accompanied by changes in lattice parameters, unit cell volume, interatomic bond lengths, and vibration mode frequencies.

The crystal structure and vibrational spectra of CoFe2O4 ferrite were studied using X-ray diffraction and Raman spectroscopy over a pressure range of 0-35GPa. A structural phase transition from the cubic Fd (3) over barm phase to the post-spinel orthorhombic Bbmm phase occurs at a pressure of approximately 23GPa through a two-phase region. Pressure-induced changes in the structural parameters, lattice distortion, and vibrational modes of the studied ferrite were investigated in detail. Lattice parameters, bond lengths, compressibility, and bulk modulus for both the cubic and orthorhombic phases of CoFe2O4 were determined.

The crystal and magnetic structures of van der Waals layered ferromagnet CrBr3 were studied using X-ray powder diffraction and neutron powder diffraction at pressures up to 23 GPa at ambient temperature and up to 2.8 GPa in the temperature range 6–300 K, respectively. The vibration spectra of CrBr3 were studied using Raman spectroscopy at pressures up to 23 GPa at ambient temperature. The anomalous pressure behavior of structural parameters and vibrational modes was observed, associated with a gradual isostructural phase transition in the pressure range 2.5–7 GPa. The Curie temperature TC reduced rapidly with a pressure coefficient dTC/dP=−4.1(4) K/GPa. A full suppression of the ferromagnetic state was expected at PC~8.4 GPa, where onset of the antiferromagnetic spin arrangement or magnetically disordered state may take place. Anomalies in Raman spectra at P~15 GPa point to another possible phase transformation in CrBr3, which may be related to the proximity of metallization of this van der Waals ferromagnet.

The crystal structure and vibrational spectra of cation-deficient nanostructured zinс ferrite Zn0.34Fe2.53☐0.13O4 (where ☐ denotes the cation vacancies) have been studied using X-ray diffraction and Raman spectroscopy methods in the pressure range of 0-34 GPa. Our results indicate a phase transition from the initial cubic phase with space group Fd m to a high-pressure phase with orthorhombic symmetry of Bbmm at pressures above 18 GPa. This phase transition is accompanied by changes in lattice parameters, unit cell volume, interatomic bond lengths, and vibration mode frequencies.

In layered perovskites with the Carpy-Galy structural type, similar structural phase transitions occur under high pressure. These structural changes, which are crucial for the pressure-induced phase transition in layered perovskite, were analyzed based on experimental X-ray diffraction data. The tilting of the Ti-O6 6 octahedra and the distortion of the arrangement of rare-earth atoms were studied in detail. Changes in these structural features in layered perovskite serve as common indicators of the phase transition to the monoclinic phase that occurs under high pressure application.

We had investigated the pressure-induced phase transition phenomenon in the perovskite-like material Nd2Ti2O7 compound. The structural and vibrational properties of a layered Nd2Ti2O7 have been studied by means of X-ray diffraction and Raman spectroscopy at pressures up to 30 GPa. The gradual structural phase transition from the initial monoclinic P21 ( C2) phase to the monoclinic P2 ( C1) phase was observed at P - 19 GPa. This pressureinduced phase transition is accompanied by anomalies in the pressure behavior of unit cell parameters and vibrational modes. The role of pressure application as a trigger for a significant rotation of the TiO6 octahedra, alterations in interatomic distances, and the displacement of Nd atoms were discussed.

In our study, we present comprehensive findings on the structural properties of Pr2Ti2O7 across a broad pressure range of 0–30 GPa. Neutron diffraction experiments, conducted under ambient conditions, offer crucial structural insights into the initial monoclinic phase with the P21 space group. As pressure increased, a significant phase transition to the monoclinic P21/m phase occurred at 13.8 GPa. Structural data analysis from X-ray diffraction highlights the essence of this transition, identifying it as the tilting of Ti-O6 octahedra. High-pressure Raman spectroscopy data unequivocally confirms the phase transition, detecting anomalies in the baric dependencies of some vibration modes of Pr2Ti2O7 and the emergence of new modes in the Raman spectra within the pressure region associated with the phase transition. The analysis of these novel vibration modes points to alterations in the Ti-O6 octahedra, emphasizing the pivotal role played by Ti4+ and O2- ions in the mechanism of the pressure-driven phase transition.

High-pressure effects on the crystal structure and vibration spectra of the perovskite-like layered La2Ti2O7 compound were studied using X-ray diffraction and Raman spectroscopy at pressures up to 30 GPa. The crystal structure of the compound was measured by means of a neutron diffraction at room temperature and ambient pressure. At P = 17.3 GPa, phase transition from the initial monoclinic phase of P21 symmetry to the monoclinic phase of P2 symmetry has been observed. The pressure-induced phase transitions in La2Ti2O7 are accompanied by anomalies in the pressure dependences of the unit cell parameters, as well as the vibrational modes. The baric dependences of lattice parameters, unit cell volume and vibration frequencies were obtained; the bulk modules for initial and pressure-induced phases of La2Ti2O7 were calculated.

The pressure response of the magnetic and structural properties of elemental holmium was explored by means of neutron powder diffraction in the pressure range up to 8.7 GPa and the temperature range 7 - 290 K. At ambient pressure, below T-N = 127 K the incommensurate helical state with a propagation vector q = (0 0 q(z)) is evidenced. On temperature lowering, the q(z) value decreases from 0.270c* (at 125 K) to 5/26c* at T-L = 20 K. Below the lock-in transition temperature T-L, a commensurate cone structure is formed due to canting of magnetic moments towards the c axis. Upon lattice compression, a gradual suppression of the low temperature cone structure was found and just a helical state was observed above 4 GPa. This state is incommensurate in the temperature range TL < T < TN and becomes commensurate below T-L. At T = 7 K, the q(z) component evolves towards 1/4 c* value at 8.7 GPa. The Neel temperature decreases to 108 K with a pressure increase up to 8.7 GPa with a pressure coefficient dT(N)/dP approximate to -2.2 K/GPa, while the lock-in transition temperature exhibits opposite behavior and grows up to about 50 K with a coefficient of dT(L)/dP approximate to 3.4 K/GPa. The magnetic P-T phase diagram of Ho is constructed. The compression of Ho lattice at T = 7 K is nearly isotropic, as found from about the same compressibilities of the alpha and c axes.

The article provides an overview of modern cements used in dentistry with an emphasis on silicate cements such as mineral trioxide aggregate (MTA). The basic requirements for dental cements are given, including their safety, adhesion to tooth tissues, resistance to various influences and thermal properties. The article analyzes in detail the composition and properties of industrial white Portland cement used in construction, in comparison with the characteristics of dental silicate cements. The general issues of the synthesis of high-base calcium silicates used in dentistry are considered from the standpoint of the chemical technology of Portland cement. The mineralogical composition and hydration processes of various cement components, their effect on tooth color and other properties are discussed. The methods of reducing the temperature and increasing the rate of formation of calcium silicates, common in the technology of dental cements and in the production of Portland cement, are indicated. It is assumed that it is possible to accelerate solid-phase synthesis in the range of 1250-1350 °C with a special method of introducing mineralizers proposed at the V.G. Shukhov BSTU for the synthesis of white Portland cement, provided it is adapted for dental formulations.

A relationship between evolution of the long-range magnetic order, crystal structure, and lattice distortions in LaMnO3 was studied by a combination of neutron diffraction and Raman spectroscopy at high pressures up to 39 and 50 GPa, respectively, covering the temperature range 5 to 290 K. The Raman spectra reveal a gradual structural phase transformation evolving in the pressure range of 4 to 17 GPa, caused by a modification of the Jahn-Teller (JT) lattice distortions from the static cooperative character to the local one. A presence of residual JT-distorted regions associated with the initial phase is detected up to 32 GPa, where the insulator-metal transition occurs. At higher pressure, the local JT distortions also vanish completely at further compression up to 50 GPa. In the neutron diffraction data, a strong suppression of the A-type antiferromagnetic (AFM) phase is observed over the pressure region of the phase transformation. This is accompanied by a noticeable reduction in magnitude of the Q2 and Q3 JT local modes. The effective ordered magnetic manganese moment is reduced about twice at pressures up to 14 GPa. At higher pressures up to 30 GPa, residual regions of the A-type AFM phase coexist with the magnetically disordered phase. In the range 30 to 39 GPa, i.e., during the pressure-induced insulator-metal transition, these regions disappear and, finally, the magnetically disordered metallic phase becomes the only ground state. The possible models of the insulator-metal transition in LaMnO3 are analyzed.

The article presents the results of an analytical review of the literature on glass ionomer (glass polyalkenate) cements, which are widely used in dentistry. This materials consist from the powder and liquid, which form a plastic mass at mix that sets to form a solid. The composition of the powder and liquid components of glass ionomer cement has been analyzed. The solid component is powdered calcium or strontium aluminofluorosilicate glass, the liquid component is an aqueous solution of acrylic acid homopolymer or its copolymer with methylene-succinic acid, maleic acid and other monomers. Information about the range of compositions of aluminofluorosilicate glass, raw materials and melting process parameters are represented. An analysis of the curing mechanism of this dental material is also carried out. Acid-base interaction and cross-linking of polymeric acid molecules with ions extracted from glass occur at mixing the powder and liquid components. The final microstructure of the hardened glass ionomer cement is partially decomposed glass particles embedded in a matrix of calcium and aluminum polyalkenoates and coated with a layer of silica gel. The information presented in this review may be useful for a comprehensive understanding by dentists, developers of dental materials and scientific groups conducting research in this subject area of the physicochemical process of curing this material.

Mn3O4 represents a model system for probing geometrically frustrated magnetism, and studying the magnetic behavior of the material under high pressure could yield new insights into the magnetostructural coupling and structurally driven magnetic ordering transitions that are otherwise not observable at ambient pressure. We report here a systematic study of the crystal and magnetic structures of Mn3O4 at high pressure up to 37 and 20 GPa using x-ray and neutron powder diffraction techniques, respectively. We find that upon compression, the crystal structure transforms from the initial tetragonal hausmannite phase of I41/amd symmetry into the orthorhombic CaMn2O4-type (Pbcm symmetry) phase via the intermediate orthorhombic CaTi2O4-type (Bbmm symmetry) phase. In the tetragonal phase, the application of pressure, P > 2 GPa, leads to the suppression of low-temperature incommensurate and commensurate antiferromagnetic (AFM) orders with a propagation vector k = (0, - 0.5, 0), and the expansion of the Yafet-Kittel-type ferrimagnetic phase, becoming the only ground state. As a result, the magnetic ordering temperature TN increases rapidly, from -43 K at P = 0 GPa to -100 K at P = 10 GPa. In the orthorhombic CaMn2O4-type phase, the AFM ordering on the sublattice of Mn3+ spins with a propagation vector k = (1/2, 0, 0) occurs below TN = 275 K for P = 20 GPa. This value of TN is about six times greater than that obtained at ambient pressure for the tetragonal phase, indicating a strong pressure enhancement of the magnetic ordering temperature in Mn3O4. These experimental observations have been complemented by density functional theory calculations, which shed light on the underlying mechanisms of the structurally coupled magnetic phenomena in geometrically frustrated magnetic systems under high pressure.

The magnetic and structural properties of elemental thulium were studied by means of neutron powder diffraction at pressures up to 5.5 GPa in the temperature range 7 - 290 K. At ambient pressure below TN = 52 K, the incommensurate magnetic state with a longitudinal sinusoidal modulation and propagation vector q = (0, 0, qz) was formed. The qz value increases on cooling from 0.279(2) and reaches the commensurate value of 2/7 at the temperature T1 = 24 K. The new magnetic arrangement is of an antiphase domain structure, composed of structural blocks involving three or four hexagonal layers with magnetic moment directions parallel within a given block and oppositely alternating from block to block along the c axis. Under high pressure, the TN value increases slightly up to 57 K at 5.5 GPa with a pressure coefficient dTN/dP = 0.9 K/GPa. The pressure dependence of the T1 temperature is more pronounced with a pressure coefficient dT1/dP = 2.9 K/GPa. The arrangement of commensurate magnetic structures formed below T1 is strongly pressure dependent. A formation of the complex magnetic states composed of structural blocks involving three or four hexagonal layers with magnetic moment signs alternating from block to block along the c axis with qz = 7/23 at 2 GPa and qz = 7/22 at 5.5 GPa was observed. The lattice compression of Tm at T = 7 K demonstrates a weak anisotropy with the most compressible c axis.

The goal of this article is to describe the new neutron imaging facility constructed on the 5th radial beamline of the WWR-SM research reactor at the Institute of Nuclear Physics of the Academy of Sciences of the Republic of Uzbekistan (Tashkent, Republic of Uzbekistan). The neutron beam with the dimensions of 90 × 90 mm2 is formed by the collimator system, the characteristic parameter L/D is 600. The two mirror detector system is based on the 6LiF/Zn(Cd)S:Ag scintillation screen and the high-resolution ProLine PL-09000 CCD camera. The design of the experimental facility, the main parameters, and recently obtained results of the neutron radiography and tomography experiments are presented.

The two-dimensional van der Waals (vdW) magnets retaining magnetic order in atomically thin limit demonstrate challenging physical phenomena and they are considered as prospective building blocks for construction of advanced spintronics and nanoelectronics devices. Here, we present experimental evidence for negative thermal expansion of lattice volume and vdW layers and strong spin–phonon coupling effects, caused by formation of the long-range ferromagnetic order in the vdW material CrBr 3 . The neutron and X-ray diffraction measurements revealed anomalous temperature variation of lattice parameters and interatomic distances and angles in the vicinity of Curie temperature ( T C ). A pronounced rise of the frequencies of the most of the observed vibrational modes and unusual reversal broadening of their full widths at half maximum below T C was found from Raman spectroscopy measurements.