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This work aims at synthesizing by reaction in the solid state orthophosphate type compounds usable in different applications (electrochemical performances, laser materials, magnetic materials, ionic conductors, potential in optics, catalysts, sensors, ceramics, etc.). The optimal operating conditions have been determined. The characterization of the materials obtained was carried out from a structural point of view by X-ray diffraction, Raman, and infrared spectroscopies, and morphologically, by scanning electron microscopy coupled with analysis by energy dispersive X-ray spectroscopy and transmission electron microscopy. The Rietveld procedure was used for the refinement investigation, and the findings reveal that the observed and calculated patterns are in excellent agreement. In the complete composition range (0 ≤ x ≤ 2), the Ba2 − xPbxSr(PO4)2 compounds crystallize in the hexagonal system at space group R 3 ¯ m with multiple units per crystal lattice Z = 3 and produce a solid solution. In solid solutions, the a and c lattice parameters varied, with a reduction in the a and c parameters proportional to the radius of the corresponding replaced ions. The M(1) and M(2) positions in the lacunar anionic orthophosphate structure were shown to be preferentially occupied by Pb2+/Ba2+/Sr2+ ions in solid solutions. The vibrational spectra of this solid solution series of crystalline orthophosphate are assigned by comparison with other orthophosphate materials and interpreted based on factor group analysis in space group R 3 ¯ m (D3d5). Raman and IR spectroscopy studies give results justifying the crystal symmetry already demonstrated by X-ray diffraction. [ABSTRACT FROM AUTHOR]

In this work, the structural, electronic, magnetic, and electrical properties of tri-layered SrMO3/BaTiO3/SrMO3 (M = Ru and Os) have been investigated using first-principles calculations based on density functional theory in the framework of GGA + U. The interfacial separation work indicates that the studied tri-layers are energetically stable. Moreover, the simultaneous presence of spontaneous polarization and magnetization with matallic characteristics was predicted. In addition, the electrical and thermal conductivities as a function of temperature are obtained using the semi-classical Boltzmann transport theory. The obtained results make the studied systems promising materials for spintronic applications. [ABSTRACT FROM AUTHOR]

Calcium manganite (CaMnO3−δ) has been extensively utilized in many applications due to its unique physical and chemical properties. In this study, the effect of Sr-substitution at the Ca-site on the structural, magnetic, electronic and electrical properties of CaMnO3 manganite perovskites is investigated in detail. The perovskite compounds Ca1−xSrxMnO3−δ (x = 0, 0.25, 0.5, 0.75 and 1) were synthesized through the sol–gel method at 1200 °C. From the patterns of X-ray diffraction, it was observed that all of the synthesized compounds show a pure perovskite phase at room temperature. The refinement results of the perovskite series suggest that a structural transformation from an orthorhombic (Pnma) to a hexagonal (P63/mmc) system occurred for 0.50 < x ≤ 0.75. We note however that the sample with the composition x = 0.50 showed a phase mixture of orthorhombic (Pnma) and hexagonal (P63/mmc). Based on DFT calculations, we have demonstrated the energetic stability of all compounds by negative formation energy and confirmed the semiconductor behavior by the presence of a band gap. The change in the band gap value with the Sr content suggests the potential tuning of the electronic behavior of CaMnO3–SrMnO3 solid solution. Furthermore, as the temperature increases from 300 to 1000 K, the electrical resistivity exhibits a reduction while the Seebeck coefficient (S) shows an augmentation. The negative values of S indicated the n-type-semiconductor nature of all compounds. The obtained values of the activation energy from thermal evolution of resistivity suggested that the electrical transport behavior of all the compounds followed the mechanism of small polaron hopping. Power factor is greatly affected by the Sr amount and reached a maximum value at x = 0.50. Overall, introducing Sr into the CaMnO3−δ matrix improved the power factor and reduced electrical resistivity. According to the obtained results, the studied manganite perovskites could be proposed as suitable materials for photocatalytic and thermoelectric applications. [ABSTRACT FROM AUTHOR]

The synthesis of [Ti.sub.3]Al[([C.sub.0.5],[N.sub.0.5]).sub.2] belonging to the [M.sub.n+1]A[X.sub.n] family of ternary layered carbides and nitrides is described. It is shown that in the case of [Ti.sub.n+1]Al[C.sub.n] MAX-phases, replacing C by N has resulted in the decrease in both lattice parameters and bulk moduli.

Raman spectra of synthetic HfSi[O.sub.4] were determined to pressures of 38.2 GPa. Changes in the spectra indicate that HfSi[O.sub.4] undergoes a room-temperature phase transition from the hafnon structure ([I4.sub.1]/amd space group) to the scheelite structure ([I4.sub.1]/a space group) at a pressure of ~19.6 GPa. Upon release of pressure to ambient conditions, the spectra indicate that the sample retains the scheelite structure. Zircon has been classified previously as the least compressible tetrahedrally coordinated silicate known. However, pressure derivatives of the peak positions in hafnon are smaller than those in zircon, and suggest that hafnon is more incompressible than zircon. Furthermore, the pressure derivatives also suggest that the high-pressure, scheelite-structured HfSi[O.sub.4] phase is more incompressible than the scheelite-structured ZrSi[O.sub.4] (reidite). Thus, the post-hafnon phase appears to be even more incompressible than hafnon, which would make it the least compressible tetrahedrally coordinated silicate known to date. Keywords: Raman Spectroscopy, hafnon, phase transformation, scheelite-structured HfSi[O.sub.4]

In this paper we report on the synthesis of a composition, Ti3Al(C0.5,N0.5)2, belonging to the Mn+1AXn family of ternary layered carbides and nitrides. X-ray and selected area diffraction confirm that this compound is isostructural with Ti3SiC2; its a and c-lattice parameters are 3.0404(5) and 18.414(6) Å, respectively. Chemical analysis performed by electron dispersive and electron energy loss spectroscopy confirmed the Ti3AlCN chemistry. Using a synchrotron radiation source and a diamond anvil cell, we also measured the pressure dependencies of the lattice parameters. Up to a pressure of ≈50 GPa, no phase transformations were observed. The bulk modulus is 219±4 GPa, with a pressure derivative, Ko′, of 3.7±0.3. We also fabricated the ternary Ti3AlC2, with some Sn [nominal composition Ti3(AlSn0.2)C2]. Its a and c-lattice parameters are 3.0804(7) and 18.5426(7) Å, respectively. Its bulk modulus is 226±3 GPa, with a pressure derivative, Ko′, of ≈4. In both cases, the compressibility was greater along the c than along the a axes. We also show that in the case of Tin+1AlCn MAX-phases, replacing C by N results in a decrease in both lattice parameters and bulk moduli. The apparent contradiction inherent in this observation can be reconciled by assuming that the addition of N results in the formation of vacancies on the Al and/or X-sites. [ABSTRACT FROM AUTHOR]

In this paper we report on the synthesis of a composition, Ti3Al(C0.5,N0.5)2, belonging to the Mn+1AXn family of ternary layered carbides and nitrides. X-ray and selected area diffraction confirm that this compound is isostructural with Ti3SiC2; its a and c-lattice parameters are 3.0404(5) and 18.414(6) Å, respectively. Chemical analysis performed by electron dispersive and electron energy loss spectroscopy confirmed the Ti3AlCN chemistry. Using a synchrotron radiation source and a diamond anvil cell, we also measured the pressure dependencies of the lattice parameters. Up to a pressure of ≈50 GPa, no phase transformations were observed. The bulk modulus is 219±4 GPa, with a pressure derivative, Ko′, of 3.7±0.3. We also fabricated the ternary Ti3AlC2, with some Sn [nominal composition Ti3(AlSn0.2)C2]. Its a and c-lattice parameters are 3.0804(7) and 18.5426(7) Å, respectively. Its bulk modulus is 226±3 GPa, with a pressure derivative, Ko′, of ≈4. In both cases, the compressibility was greater along the c than along the a axes. We also show that in the case of Tin+1AlCn MAX-phases, replacing C by N results in a decrease in both lattice parameters and bulk moduli. The apparent contradiction inherent in this observation can be reconciled by assuming that the addition of N results in the formation of vacancies on the Al and/or X-sites. [ABSTRACT FROM AUTHOR]