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Understanding the thermal properties of zeolites is crucial for their industrial applications. This study explores the thermal stability and dehydration process of clinoptilolite using high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Clinoptilolite’s thermal decomposition was monitored from 25 °C to 1200 °C, with results analyzed based on its crystal structure. Principal components analysis (PCA) of the DRIFT spectra indicated progressive water removal and dehydration upon heating, leading to the formation of hydrogen bonds. Thermogravimetric analysis (TGA) revealed a two-step endothermic weight loss: initially, physically adsorbed water was lost up to 100 °C, followed by the removal of tightly bound water and hydroxyl groups until 800 °C. Clinoptilolite remained the dominant phase up to 800 °C, after which albite and cristobalite took over. Rietveld refinement showed that the sample initially contained 70% clinoptilolite, 24% albite, and 6% cristobalite. Above 800 °C, clinoptilolite disappeared, leaving 93% albite and 7% cristobalite. FT-IR spectra changes due to water loss were evident: drying of adsorbed water occurred up to 75 °C and minimal changes were observed from 75 °C to 135 °C, followed by further dehydration until 240 °C. Complete dehydration was confirmed by the disappearance of OH stretching vibration bands by 395 °C, consistent with TGA findings.

Multiferroic 0.5BiFeO3-0.5Pb(Fe0.5Ta0.5)O3 solid solution is a material that exhibits ferroelectric and antiferromagnetic orderings in ambient temperature. The solid solution was obtained as a result of a conventional reaction in a solid state. The obtained material is a dense, fine-grained sinter whose surface was observed by scanning electron microscopy (SEM) and stoichiometry was confirmed by energy dispersive X-ray spectroscopic (EDS) analysis. According to the X-ray powder diffraction (XRD) measurements, the main phase is R3c space group with admixture of Pm-3m regular phase. Small contribution of pyrochlore-like phase was also observed. Mössbauer spectroscopy suggested random distribution of Fe3+/Ta5+ cations in the B sites of ABO3 compound. Reduction of the magnetic hyperfine field with an increase in the substitution of Ta5+ in Fe3+ neighbourhood was also observed.

Magnesium oxide (MgO) is one of the most important raw materials in many branches of industry. Magnesium oxide is a popular refractory raw material because of its high refractoriness and high resistance to basic slags and environment. In many cases, use of MgO is limited by its properties, especially the presence of secondary phases like iron oxides. The amount and distribution of iron oxides can strongly influence the technological properties of MgO and depend on the manufacturing method, particularly the heat-treatment process. The aim of the study was to evaluate the influence of the heat-treatment process on amount and distribution of iron ions in a magnesium oxide lattice. The 57Fe Mössbauer effect measurements of fused and sintered magnesium oxide samples doped by the iron oxide were conducted. Investigation reveals in both cases the presence of Fe2+ as well as Fe3+ ions. Fe2+ ions occupy Mg2+ octahedral sites in the MgO lattice, whereas the Fe3+ ions are located in highly distorted octahedral coordination. The amount of Fe2+ varies from around 66% for fused samples to 30% for sintered samples.

Abstract: Calcium zirconate (CaZrO3), because of its high melting point, low thermal expansion coefficient, high strength and excellent corrosion resistance against alkali oxides, is a good candidate for a novel refractory material. CaZrO3 is mostly synthesized by the reaction in the solid state but the material obtained in such a way often suffers low bulk density, high porosity and other defects which lower its potential application value. To overcome these obstacles a novel synthesis method by an electric arc melting technique was proposed. The crystal structure of melted CaZrO3 was compared with a conventionally synthesized material. According to X-ray measurements the obtained material has an orthorhombic perovskite-like structure. Its stoichiometry was confirmed by the scanning electron microscope and EDS analysis. The material is almost poreless with its density close to theoretical. The estimated crystal structure parameters were used to calculate the electronic structure of CaZrO3 using the full potential linear augmented plane wave (FLAPW) method. It has been found that CaZrO3 is an insulator with the energy band gap of 4.1eV. The Ca–O bond is typically ionic while Zr–O bond is of a significant covalent character. [Copyright &y& Elsevier]

Abstract: This paper concerns synthesis, X-ray analysis (300K), electrical resistivity and 57Fe Mössbauer effect studies (4.2K) of complete Tb0.27Dy0.73(Mn1−x Fe x )2 intermetallic series, with a borderline compound Tb0.27Dy0.73Fe2 known as Terfenol-D. A cubic Laves phase Fd3m of the MgCu2-type is observed across the series. The lattice parameter decreases parabolically with x. Electrical resistivity was measured in a wide temperature region across the Tb0.27Dy0.73(Mn1−x Fe x )2 series and the parameters which characterize resistivity dependence on temperature, including Debye temperature, were determined. Residual, phonon and magnetic contributions were separated from electrical resistivity. The magnetic contribution to electrical resistivity was applied to estimate Curie temperatures. The Curie temperature increases significantly with x. 57Fe Mössbauer effect measurements for the Tb0.27Dy0.73(Mn1−x Fe x )2 intermetallic system evidence an [100] easy axis of magnetization. Mn/Fe substitution introduces a local area, at sub-nanoscale, with different Mn/Fe neighbourhoods of the tested 57Fe atoms. Hyperfine interaction parameters, an isomer shift, a magnetic hyperfine field and a quadrupole interaction parameter were determined from the spectra both for the local neighbourhood area and, as averaged values, for the sample as bulk. The average magnetic hyperfine field increases parabolically with x. The correlation between Curie temperatures and magnetic hyperfine fields is discussed. [ABSTRACT FROM AUTHOR]

The synthesis of materials and the studies of crystal structure and Fe Mössbauer effect were performed for TbDy(FeCo) intermetallics. Terfenol-D (TbDyFe) is the starting compound of this Fe/Co-substituted series. X-ray measurements showed evidence of a pure cubic Laves phase C15, MgCu-type, and unit cell parameters were determined across the series. A Co substitution introduced local area, at sub-nanoscale, with random Fe/Co neighbourhoods of the Fe atoms. Mössbauer effect spectra for the TbDy(FeCo) series at room temperature are composed of a number of locally originated subspectra due to the random distribution of Fe and Co atoms in the transition metal sublattice, and due to [1 1 1] an easy axis of magnetization. Isomer shift, magnetic hyperfine field and quadrupole interaction parameter were obtained from the spectra, both for the local area and for the bulk sample. As a result of Fe/Co substitution, a Slater-Pauling-type curve for the average magnetic hyperfine field vs. Co content was observed. It was found that the magnetic hyperfine fields corresponding to the local area also create a dependence of the Slater-Pauling-type vs. Co contribution in the Fe/Co neighbourhoods. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis and X-ray analysis (300 K) of a new series were performed. The lattice parameter is considerably reduced with x. Electrical resistivity for the intermetallic series was measured in a wide temperature range and the parameters characterising the dependence of resistivity on temperature and composition were determined. The magnetic part of the resistivity was used to estimate Curie temperatures. The Curie temperature is strongly increased as a result of Mn/Co substitution. The obtained -results are related to the data known for the and series. [Copyright &y& Elsevier]

Abstract: Electrical resistivities of the Dy(Fe1−x Co x )2 intermetallic series were measured in a wide temperature region and the residual, phonon and magnetic contributions to the resistivities across the series were determined. The magnetic ordering temperatures were estimated for the Dy(Fe1−x Co x )2 compounds using the magnetic contribution to the electrical resistivity. The splitting energies between the 3d subbands of iron for the Dy(Fe1−x Co x )2 series were estimated using the magnetic hyperfine fields at 57Fe nuclei. The Curie temperatures obtained for the Dy(Fe1−x Co x )2 intermetallics and the Curie temperatures reported in the literature for the Dy(Mn1−x Fe x )2 and Dy(Mn0.4−x Al x Fe0.6)2 series correlate linearly with the squared energy splitting between the 3d subbands. [Copyright &y& Elsevier]

It was previously found that the magnetic hyperfine fields observed at 57Fe nuclei (4.2 K) in the Dy(Mn1-xFex)2 and Dy(Fe1-xCox)2 intermetallics form a Slater–Pauling curve. Both 3d subbands in the Dy(Mn0.4Fe0.6)2 compound are filled up only partially with 3d electrons. The consequence of Mn/Al substitution, in the Dy(Mn0.4Fe0.6)2 compound was studied in the present paper. For this purpose the synthesis and X-ray analysis (300 K) of the series Dy(Mn0.4-xAlxFe0.6)2 were performed. The cubic, MgCu2-type Fd3m crystal structure was observed across the series. Nevertheless for x=0.35 and 0.40 a stoichiometric admixture of the hexagonal, MgZn2-type, P63/mmc was evidenced. 57Fe Mössbauer effect measurements for the series were performed at 4.2 K. The magnetic hyperfine fields form a separate branch of the Slater–Pauling curve. This branch is compared to the magnetic hyperfine field previously obtained for the Dy(Mn0.4Fe0.6-xAlx)2 series (the Fe/Al substitution). The possible 3d electron band structure is discussed qualitatively within the Stoner model. [Copyright &y& Elsevier]

It was previously found, that the magnetic hyperfine fields observed at 57Fe nuclei (4.2 K) in the Dy(Mn1-xFex)2 and Dy(Fe1-xCox)2 intermetallics form a Slater–Pauling curve. Both 3d sub-bands in the Dy(Mn0.4Fe0.6)2 compound are filled up only partially with 3d electrons. The consequence of Fe/Al substitution, in the Dy(Mn0.4Fe0.6)2 compound, was studied in the present paper. For this purpose the synthesis and X-ray analysis (300 K) of the series Dy(Mn0.4Fe0.6-xAlx)2 were performed. The cubic, MgCu2-type, Fd3m crystal structure was observed across the series. 57Fe Mössbauer effect measurements for the series were realized at 4.2 K. The obtained crystallographic data and the hyperfine interaction parameters are presented. The magnetic hyperfine fields form a separate branch of the Slater–Pauling curve. The data are qualitatively related to the Stoner model. [Copyright &y& Elsevier]

It was previously found that the magnetic hyperfine fields observed at 57Fe nuclei (4.2 K) in the Dy(Mn1−xFex)2 and Dy(Fe1−xCox)2 intermetallics form a Slater–Pauling curve with a maximum hyperfine field for the Dy(Fe0.7Co0.3)2 compound. The Fe/Al substitution in the Dy(Fe0.7Co0.3)2 compound was studied in the present paper. The intermetallic series Dy(Fe0.7−xAlxCo0.3)2 was prepared and data of an X-ray analysis are presented (300 K). The cubic, MgCu2-type, Fd3m crystal structure was observed. 57Fe Mo¨ssbauer effect measurements for the series were performed (4.2, 77, 293 K) and the obtained hyperfine parameters are presented. The magnetic hyperfine fields form a separate branch of the Slater–Pauling curve. The data related to a possible band structure are qualitatively discussed within the frame of the Stoner model. [Copyright &y& Elsevier]

MgO–ZrO 2 ceramics were obtained by three different methods: conventional sintering, arc melting and field assisted sintering. The present study was undertaken in order to determine the influence of the different sintering techniques on the structural properties of MgO–ZrO 2 ceramics. The phase compositions of the obtained samples consisted of MgO and ZrO 2 cub. ss (doped by MgO). The amount of all phases in the final product and their average crystallite sizes are strongly influenced by the sintering method. The smallest crystallites were realized for ceramics consolidated by the field assisted sintering method (20.1 ± 2.5 nm for MgO and 27.0 ± 2.7 nm for ZrO 2 cub. ss ). About ten times larger crystallites resulted by conventional sintering. The average crystallite size in the material obtained by arc melting technique was around 116 ± 20.4 nm. It was observed that the microstructures of the samples prepared by arc melting and field assisted sintering are similar. [ABSTRACT FROM AUTHOR]

Abstract: X-ray powder diffraction measurements (295K) show that the cubic, MgCu2-type, crystal structure appears in compounds. The lattice parameter is considerably and weakly nonlinearly reduced with x. The electrical resistivities of the intermetallic series were measured over a wide temperature range and the parameters characterising the dependence of resistivity on temperature and composition were determined. In order to separate the residual, phonon and magnetic contributions to total resistivity the Matthiesen formula was used. The magnetic part of the resistivity was used to estimate Curie temperatures. The Curie temperature is strongly and nonlinearly reduced as a result of Co/Ni substitution. The obtained results are related to data known for the and series. [Copyright &y& Elsevier]

Abstract: From X-ray analysis (295 K) it was found that the cubic, -type, crystal structure appears across the Gd(Fe1−x Co x )2 series. Electrical resistivity measurements for the Gd(Fe1−x Co x )2 intermetallics were performed in a wide temperature region and the parameters characterizing the resistivity dependence on temperature and composition were determined. The differential of the electrical resistivity against temperature was used to estimate Curie temperatures. The Curie temperature versus x, high and moderately increasing in the iron-rich area, rapidly drops in the cobalt-rich region. The obtained results are compared with the data known for the Dy(Fe1−x Co x )2 series. The Curie temperature is related to both the number of 3d electrons and the de Gennes factor. [Copyright &y& Elsevier]

Abstract: Synthesis, X-ray analysis (300K), electrical resistivity and Mössbauer effect studies in the intermetallic compounds Y(Fe1−x Co x )2 are reported. Cubic Laves phases MgCu2-type, were observed across the series. Crystal lattice parameter is considerably reduced with Co concentration. The lattice parameters of the Y(Fe1−x Co x )2 series are compared to analogous data previously observed for the Gd(Fe1−x Co x )2 and Dy(Fe1−x Co x )2 series. Electrical resistivity for the Y(Fe1−x Co x )2 intermetallic series was measured in the temperature range 15–1000K. Parameters characterizing the resistivity dependence on temperature including Debye temperature were determined. Residual, phonon and magnetic resistivity were separated from the measured electrical resistivity. Curie temperatures of the Y(Fe1−x Co x )2 series were determined using both electrical resistivity and Mössbauer effect measurements. The Curie temperature increases with x, reaches maximum approximately at x =0.3 and than strongly decreases as a result of Fe/Co substitution. The obtained Curie temperatures for the Y(Fe1−x Co x )2 series are related to the data known for the Dy(Fe1−x Co x )2, Gd(Fe1−x Co x )2 and other series. Numerical formula, which approximates Curie temperatures of intermetallics is proposed. [Copyright &y& Elsevier]

Abstract: Findings from X-ray powder diffraction measurements (295 K) show that the cubic, -type, crystal structure appears in compounds.The lattice parameter is considerably reduced with x. Electrical resistivity for the intermetallic series was measured in a wide temperature range and the parameters characterising the dependence of resistivity on temperature and composition were determined. The magnetic part of the resistivity was used to estimate Curie temperatures. The Curie temperature is strongly reduced as a result of Fe/Ni substitution. The obtained -results are related to the data known for the and series. [Copyright &y& Elsevier]