Copper-substituted tricalcium phosphates

Copper-substituted tricalcium phosphates (CuTCP) with different copper contents were developed using precipitation of copper-containing amorphous calcium phosphates (ACP) from salt solutions followed by heat treatment. Porous CuTCP ceramic was obtained using negative replicas. Using a set of investigation methods (powder X-ray diffraction, IR spectroscopy, ESR spectroscopy, and scanning electron microscopy), all copper-substituted tricalcium phosphates were found to have the whitlockite structure with copper incorporated in TCP in the 2+ oxidation state. The resulting material is promising for the use in regenerative medicine owing to higher solubility in body fluids compared with TCP and combination of bactericidal properties and the lack of cytotoxicity.     

High-temperature heat capacity of stannates Er<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript> and Tm<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript>

Erbium stannate Er₂Sn₂O₇ and thulium stannate Tm₂Sn₂O₇ with a pyrochlore-type structure were produced by solid-phase synthesis by calcining stoichiometric mixtures of the respective oxides in air at 1473 K for 240 and 200 h. The high-temperature heat capacity of Er2Sn2O7 and Tm₂Sn₂O₇ was studied by differential thermal calorimetry at 353–1000 K. From the experimental dependences C _P = f(T), the thermodynamic functions (enthalpy change, entropy change, and reduced Gibbs free energy) of oxide compounds were calculated.     

Ferromagnetism of GaSb (2% Mn) alloy

A polycrystalline sample of composition GaSb + 2% Mn was prepared by melt quenching. Manganese substitutes for gallium positions to form limited solid solution Ga_{1 ? x} Mn _x Sb, as shown by X-ray powder diffraction and SEM, but most manganese is consumed in the formation of magnetically ordered Mn_1.1Sb inclusions having the Curie point T _C ≈ 560 K, as shown by magnetic studies.     

Singularity in high-frequency susceptibility of thin magnetic films with uniaxial anisotropy

A sharp peak of magnetic susceptibility has been observed in the ferromagnetic resonance spectra of uniaxial magnetic films placed in a planar field directed orthogonal to the easy magnetization axis, along which a pumping high-frequency magnetic field has been oriented. The peak width is considerably narrower than the line width of the uniform ferromagnetic resonance, and its position in a field equal to the film anisotropy field does not depend on the pumping frequency. The nature of the peak is associated with a drastic increase in the static transverse susceptibility of the film in the vicinity of the anisotropy field. It is shown phenomenologically that the peak can be observed only for quality samples with small angular and amplitude dispersion of the uniaxial anisotropy.     

High-temperature heat capacity of erbium titanate with a pyrochlore structure

Erbium titanate with a pyrochlore structure has been synthesized by a ceramic method from stoichiometric Er₂O₃–TiO₂ mixtures at 1673–1773 K. The high-temperature heat capacity of Er₂Ti₂O₇ (320–1000 K) has been studied by differential scanning calorimetry. The thermodynamic functions of this oxide compound—enthalpy and entropy changes and reduced Gibbs—have been calculated from the experimental dependence C _P = f(T).     

Synthesis and magnetic properties of solid solutions In<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sb〈Mn〉

Manganese-doped solid solutions In_1–x Ga _x Sb (x = 0.05, 0.1, 0.5, 0.9, 0.95) were synthesized. It was found that, in samples of the compositions In_0.95Ga_0.05Sb〈Mn〉 and In_0.05Ga_0.95Sb〈Mn〉, a homogeneous substitutional solid solution forms, into which manganese-containing clusters are incorporated. The clusters are mainly located at crystal lattice defects—grain boundaries and dislocations. The ferromagnetic properties of the obtained samples at room temperature and higher are caused by clusters Mn_1+x Sb, the effective size of which is about 180–300 nm.     

High-temperature heat capacity and thermodynamic properties of pyrovanadate Pb<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript> and orthovanadate Pb<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The heat capacities of Pb₂V₂O₇ and Pb₃(VO₄)₂ as a function of temperature in the range 350–965 K have been studied by the differential scanning calorimetry method. The C_P = f(T) curve for Pb₂V₂O₇ is described by the equation C_p = (230.76 ± 0.51) + (73.60 ± 0.50)×10^-3T ? (18.38 ± 0.54)×10⁵T^-2 in the entire temperature range. For Pb₃(VO₄)₂, there is a well-pronounced extreme point in the C_P = f(T) curve at T = 371.5 K, which is caused by the existence of a structural phase transition. The thermodynamic properties of the oxide compounds have been calculated.     

Helium impurity nanocluster gels in superfluid helium

Rapid cooling of a helium impurity gas mixture to the superfluid helium temperatures allows us to prepare an impurity-helium condensate with jelly-like structure (impurity gel) in superfluid He-II. It is clear that the properties of these gels should be substantially different from those of a bulk impurity substance, constituting a new class of soft matter — quantum gel, where superfluid He-II filling the nanopores between the randomly connected impurity nanoclusters serves as the dispersion medium of the gel.