G. E. Nikiforova

Heat capacity and thermodynamic functions of YbPO4 from 0 to 1800 K

The thermodynamic functions of YbPO4 have been determined experimentally in the temperature range 6–1745 K. The results have been used to calculate temperature-dependent heat capacity, entropy, enthalpy increment, and reduced Gibbs energy of YbPO4 in the range 6–1800 K. The Gibbs energy of formation of ytterbium orthophosphate (ΔfG0(298.15 K)) has been determined.

High-temperature thermodynamic properties of LuPO4

The high-temperature enthalpy of lutetium orthophosphate has been determined as a function of temperature in the range 432.92–1744.58 K using drop calorimetry. The present and earlier experimental data have been used to calculate temperature-dependent heat capacity of LuPO4 in the range 1–1750 K.

Heat capacity and thermodynamic functions of Gd(VO4)0.5(PO4)0.5 solid solution in the low-temperature region

A series of Gd(VO4)1−x(PO4)x solid solutions with a xenotime structure was synthesized. The heat capacity of a Gd(VO4)0.5(PO4)0.5 solid solution sample was measured by adiabatic calorimetry in the low-temperature region (6–348 K). The thermodynamic functions were calculated within the studied temperature range.

Garnet Solid Solution (Y 1 – x Bi x ) 3 Fe 2.5 Ga 2.5 O 12

Samples of composition (Y1–xBix)3Fe2.5Ga2.5O12 (0 ≤ х ≤1), synthesized by the polyvinyl alcohol gel combustion method, have been studied by X-ray diffraction. It has been shown that the homogeneity range of the solid solution persists up to the composition Y1.5Bi1.5Fe2.5Ga2.5O12. This allows to consider gallium- substituted bismuth yttrium ferrites with an equimolar Fe: Ga ratio as stable materials for possible use in magnetooptics.

Thermodynamic properties of Dy2O3 · 2ZrO2 and Ho2O3 · 2ZrO2 in the range 10–340 K

The low-temperature heat capacity of Dy2O3 · 2ZrO2 and Ho2O3 · 2ZrO2 has been determined by adiabatic calorimetry in the temperature range 10–340 K. The results have been used to calculate the entropy, enthalpy increment, and reduced Gibbs energy of the zirconates without taking into account their low-temperature magnetic transformations.

Low-temperature heat capacity of yttrium orthotantalate

The heat capacity of yttrium orthotantalate has been determined as a function of temperature by adiabatic calorimetry in the temperature range 0–340 K. Smoothed heat capacity data have been used to calculate the thermodynamic functions of yttrium orthotantalate.

Features of Mg(Fe0.8Ga0.2)2O4 synthesis by glycine-nitrate method

A finely dispersed powder of composition Mg(Fe0.8Ga0.2)2O4 was prepared by glycine-nitrate method. The use of glycine as a reducing agent allows preparation of the product without carbon-containing admixtures with unimodal particle size distribution and lower crystallization temperature (as compared with nitrate-citrate method of Mg(Fe0.8Ga0.2)2O4 synthesis) immediately after reaction completion.

Heat capacity and thermodynamic properties of Mg(Fe0.6Ga0.4)2O4 in the 0–800 K temperature range

The heat capacity of Mg(Fe0.6Ga0.4)2O4 in the temperature range of 4.56–804.9 K is measured by adiabatic and differential scanning calorimetry. The temperature dependence of the heat capacity of Mg(Fe0.6Ga0.4)2O4 in the 0–800 K range is determined by generalizing the experimental data. The temperature dependences of thermodynamic functions (entropy, enthalpy change, and the reduced Gibbs free energy) are calculated. The abnormal contribution to the heat capacity Cpan(T) in the temperature range of 5–52 K is estimated.

Synthesis of MgFe 1.6 Ga 0.4 O 4 by Gel Combustion Using Glycine and Hexamethylenetetramine

A powderlike material of composition MgFe1.6Ga0.4O4 was synthesized by gel combustion using a glycine–hexamethylenetetramine mixture. The gel produced by the synthesis was studied by thermal analysis (TGA/DSC) and IR spectroscopy. This mixture was shown to be efficient for obtaining homogeneous nanosized MgFe1.6Ga0.4O4. The morphology of the powders was characterized by scanning electron microscopy and X-ray powder diffraction analysis.

(Y 1– x Bi x )3(Fe 1– y Ga y ) 5 O 12 Solid Solution Region in the Ieneke Diagram

Garnet ferrites with the overall composition (Y1–xBix)3(Fe1–yGay)5O12 (0 ≤ х ≤1, 0 ≤ y ≤1) have been synthesized and characterized by X-ray diffraction. A relationship has been demonstrated between an increase in the concentration of Ga3+ cations and an increase in Bi2O3 solubility in ss-Y3(Fe,Ga)5O12.