Калориметрическим методом в интервале 298.15–673 К исследованы теплоемкости ферритов GdMeFe2O5(Me Li, Na, K, Cs). На кривых зависимостей C f(T) выявлены -образные эффекты при 448 и 598 К у GdLiFe2O5, при 473 и 573 K у GdNaFe2O5, при 598 K у GdKFe2O5 и при 448 К у GdCsFe2O5, относящиеся к фазовому переходу II рода. Вычислены температурные зависимости термодинамических функций C (Т, Н°(Т)–Н°(298.15), S°(Т) и Ф**(Т. В интервале 303–493 К исследованы электрофизические характеристики синтезированных ферритов. На кривых зависимостей lg f(T), lgR f(T) обнаружены такие же эффекты, как на кривой C f(T). Выявлено, что соединения обладают полупроводниковой проводимостью. В точке Тпр у ферритов полупроводниковая проводимость переходит в металлическую и резко изменяются емкости и диэлектрические проницаемости, что можно отнести к сегнетоэлектрическим фазовым переходам (точки Кюри, Нееля) и в определенной степени выяснить природу -эффекта на кривой C f(T).

Double ferrites ErCaFe2O5.5, ErSrFe2O5.5, and ErBaFe2O5.5 were synthesized by solid-state reactions from erbium and iron(III) oxides and calcium, strontium, and barium carbonates. The compounds were found to crystallize in the orthorhombic system. Their unit cell parameters were determined by X-ray powder diffraction; their densities were measured.

Ferrites of composition ErMIFe2O5 (MI = Li, Na, K, Cs) were synthesized by a solid-phase method. The structure of the ferrites was for the first time studied by X-ray powder diffraction. Crystal systems, unit cell parameters, and X-ray and pycnometric densities were determined. For ErLiFe2O5, a = 10.510 Å, c = 14.270 Å, V∘= 1616.16 Å3, Z = 16, V subcell ∘ = 101.01 Å3, ρx = 6.01 g/cm3, ρpyc = 5.97 ± 0.04 g/cm3; for ErNaFe2O5, a = 10.519 Å, c = 15.510 Å, V∘ = 1759.56 Å3, Z = 16, V subcell ∘ = 109.90 Å3, ρx = 5.77 g/cm3, ρpyc = 5.72 ± 0.08 g/cm3; for ErKFe2O5, a = 11.050 Å, c = 15.480 Å, V∘ = 1937.33 Å3, Z = 16, V subcell ∘ = 121.08 Å3, ρx = 5.46 g/cm3, ρpyc = 5.41 ± 0.04 g/cm3; and for ErCsFe2O5, a = 10.78 Å, c = 16.01 Å, V∘ = 1905.37 Å3, Z = 16, V subcell ∘ = 119.09 Å3, ρx = 6.86 g/cm3, ρpyc = 6.61 ± 0.01 g/cm3.

The GdMCr2O5 (M=Na, K, Cs) chromites are synthesized from Gd2O3, Cr2O3, and M2CO3 by solid-state reactions and are shown to have a tetragonal structure. The heat capacity of the chromites is measured from 298.15 to 673 K using a heat-pulse calorimeter. The data for GdKCr2O5 and GdCsCr2O5 show anomalies at 373 and 398 K, respectively, attributable to a second-order phase transition. The best fit equations for the C p 0 (T) data are derived. Electrical measurements in the range 303–383 K attest to semiconducting behavior of the chromites.

Ferrites YbSrFe 2 O 5.5 and YbBaFe 2 O 5.5 are prepared by reacting ytterbium(III) oxide and iron(III) oxide with strontium or barium carbonate in the solid phase. The ferrites crystallize in the orthorhombic system as shown by indexing of their X-ray diffraction patterns with homology modeling: for YbSrFe 2 O 5.5 , a = 10.74 ± 0.006 Å, b = 10.93 ± 0.006 Å, c = 16.64 ± 0.046 Å, V 0 = 1953.3 Å 3 , Z = 16, V subcell 0 = 122.08 Å 3 , ρ X-ray = 6.26 g/cm 3 , ρ pycn = 6.18 ± 0.9 g/cm 3 ; for YbaBaFe 2 O 5.5 , a = 10.74 ± 0.013 Å, b = 10.99 ± 0.004 Å, c = 17.16 ± 0.017 Å, V 0 = 2025.4 Å 3 , Z = 16, V subcell 0 = 126.59 Å 3 , ρ X-ray = 6.69 g/cm 3 , ρ pycn = 6.40 ± 0.32 g/cm 3 . The calorimetric heat capacities of the ferrites are studied from 298.15 to 673 K. The C p o ∼ f ( T ) curves show λ peaks at 448 K for YbSrFe 2 O 5.5 and at 373 K for YbBaFe 2 O 5.5 , likely, due to second-order phase transitions. The dielectric constants and electrical resistances of the ferrites are studied as functions of temperature from 293 to 493 K.

Ceramic samples of ferrites with the composition (YbMFe2O5.5)-Fe-II (M-II = Mg, Ca) are prepared from ytterbium(III) oxide, iron(III) oxide, and alkaline-earth carbonates. These ferrites crystallize in an orthorhombic system with the following unit cell parameters: for YbMgFe2O5.5, a = 10.72 Angstrom, b = 10.98 Angstrom, c = 14.17 Angstrom, V-0 = 1667.8 Angstrom(3), V-subcell(0) = 104.24 Angstrom(3), Z = 16, rho(X-ray) = 6.32 g/cm(3), rho(meas) = (6.31 +/- 0.01) g/cm(3); for YbCaFe2O5.5, a = 10.74 Angstrom, b = 11.12 Angstrom, c = 15.13 Angstrom, V-0 = 1806.9 Angstrom(3), V-subcell(0) = 112.93 Angstrom(3), Z = 16, rho(X-ray) = 6.07 g/cm(3), rho(meas) = (5.83 +/- 0.25) g/cm(3). The heat capacities of the ferrites are measured versus the temperature using dynamic calorimetry in the range from 298.15 to 673 K. The thermodynamic functions are calculated: Cp-0(T), H-0(T) - H-0(298.15), S-0(T), and Phi**(T).

The method of dynamic calorimetry is used to investigate the heat capacity of chromite NdLiCr2O5 in the temperature range from 298 to 673 K. A λ-like peak is observed at 523 K.The equations of temperature dependence of the heat capacity of this chromite are derived.The temperature dependences of the thermodynamic functions are calculated.The results of electrophysical investigations indicate that this compound may be classed with semiconductors.

A new chromite GdBaCr2O5.5 was synthesized by ceramic technology and characterized using X-ray powder diffraction. The compound crystallizes in a tetragonal crystal system with a = 10.77 angstrom, c = 17.90 angstrom, V = 2076.3 angstrom(3), Z = 16, V-subcell = 129.8, angstrom(3), rho(x-ray) = 6.22 g/cm(3), rho(pycn) = (6.17 +/- 0.04) g/cm(3). The heat capacity for the new chromite was experimentally determined in the range from 298.15 to 673 K, equations for the heat capacity were derived, and the thermodynamic functions C degrees(p) (T), H degrees(T) - H degrees(298.15), S degrees(T), and P Phi**(T) were calculated. Second-order phase transitions at 348 and 548 K were found in the heat capacity trend, which are likely due to the paramagnetism of gadolinium ions. The dielectric constant and electrical resistance C, versus temperature measurements showed several features that are in correlation with the calorimetric heat capacity measurements and prove that the chromite has semiconductor properties.

The solid-phase method is used to synthesize GdCaCr 2 O 5.5 chromite from chrome and gadolinium oxides and calcium carbonate. X-ray phase analysis is used to find that the compound is crystallized in tetragonal crystal system with the following lattice parameters: a = 10.77 Å, c = 15.84 Å, V = 183.3 Å 3 , Z = 16, V unit cell = 11.8 Å, ρ X-ray = 5.63, and ρ pycn = 5.55+0.05 g/cm 3 . An IT-S-400 calorimeter is used to measure the heat capacity of the compound in the temperature range from 298.15 to 673 K. Pronounced anomalous jumps are observed on the heat capacity curve at 448 and 473 K, which are apparently associated with second- order phase transitions. Equations describing the C p ≈ f ( T ) dependence are derived, and the functions C p ( T ), S ( T ), H ( T ) - H (298.15), and Φ xx ( T ) of chromite in the range from 298.15 to 673 K are calculated. The temperature dependences of dielectric permittivity and electric resistance of the compound are investigated in the range from 303 to 383 K to demonstrate that chromite under investigation exhibits semiconductor properties.

The manganites (MMgDyMn2O6)-Mg-1 (M-I = Li, Na, K, Cs) were synthesized by solid-state annealing from dysprosium oxide, manganese oxide, magnesium carbonate, and alkali metal carbonate. According to X-ray diffraction, these compounds crystallize in the orthorhombic system with the following unit cell parameters : LiMoDyMn2O6, a = 10.54 Angstrom, b = 10.72 Angstrom, c = 17.08 Angstrom, Vdegrees = 1929.9 Angstrom(3), V(cell)degrees =120.6 Angstrom(3), Z = 16, rho(x) = 5.49 g/cm(3), rho(pycn) = (5.30 +/- 0.06) g/cm(3); NaMgDyMn2O6, a = 10.55 Angstrom, b = 10.73 Angstrom, c = 16.92 Angstrom, Vdegrees = 1915.4 Angstrom(3), V(cell)degrees = 119.7 Angstrom(3), Z = 16, rho(x) = 5.76 g/cm(3), rho(pycn) = (5.65+/-0.09) g/cm(3); KMgDyMn2O6, a = 10.60Angstrom, b = 10.75Angstrom, c = 16.83 Angstrom, Vdegrees = 1917.1 Angstrom(3), V(cell)degrees = 119.8 Angstrom(3) Z=16, rho(x) = 5.98 rho(pycn) = (5.90+/-0.05) g/cm(3); CsMgDyMn2O6, a = 10.56 Angstrom, b = 10.74 Angstrom, c = 17.02 Angstrom, Vdegrees = 1930.3 Angstrom(3), Vdegrees(cell) = 120.6 Angstrom(3), Z = 16, rho(x) = 7.23 g/cm(3) rho(pycn) = (7.14 +/- 0.07) g/cm(3).

Chromite GdMgCr2O5.5 was synthesized by solid-phase technology from chromium(III) and gadolinium oxides and magnesium carbonate. X-ray powder diffraction showed that the compound crystallizes in the tetragonal crystal system. The unit cell parameters are the following: alpha = 10.79 Angstrom, c = 16.54 Angstrom, V = 1925.7 Angstrom(3), V-u.c. = 120.4 Angstrom(3), Z = 16, rho(x-ray) = 5.15 g/cm(3), and rho(pyen) (5.09 +/- 0.08) g/cm(3). The heat capacity of the compound was measured on an IT-S-400 calorimeter in the range of 298.15-673 K. Abrupt anomalous jumps have been found in the C-p(0) similar to f(T) curve at 448 and 498 K. These jumps are apparently associated with second-order phase transitions. The equations describing the C-p(0) similar to f(T) dependence were derived, and the functions C-p(0)(T), S-0(T), H-0(T) - H-0(298.15), and Phi(xx)(T) were calculated for the chromite in the range 298.15-673 K. The chromite dielectric constant was investigated as a function of temperature. It has been found that this compound possesses a high dielectric constant and has several specific features in agreement with its heat capacity in the range 298.15-673 K.

The NdMFe2O5 (M = Li, Na, K, Cs) ferrites are prepared by solid-state reactions using mixtures of Nd2O3 , Fe2O3 , and M2CO3 . The ferrites are shown to have a tetragonally distorted perovskite structure (Z= 16) with the following lattice parameters: a = 10.94 Å, c = 13.83 Å,V = 1655.2 Å3 for NdLiFe2O5; a= 10.98 Å, c = 15.10 Å, V = 1820.5 Å3 for NdNaFe2O5; a= 10.96 Å, c = 16.82 Å, V= 2020.5 Å3 for NdKFe2O5; a= 10.93 Å, c= 17.94 Å, V = 2143.2 Å3 for NdCsFe2O5 .

NdMCr2O5 (M = Na, K, Cs) and NdMgCr2O5.5 are prepared by solid-state reactions between appropriate oxides and carbonates and are shown to have a tetragonal structure. The heat capacity of these chromites, measured from 298.15 to 673 K, exhibits sharp changes attributable to second-order phase transitions. The Cp0(T) data are represented by quadratic best fit equations. The electrical resistivity of the chromites is measured between 303 and 493 K. The results attest to semiconducting behavior of the materials in certain temperature ranges.

A mixed manganite of composition LaLiSrMn2O6 , with a cubic structure, is synthesized for the first time by solid-state reactions, using mixtures of appropriate carbonates and oxides, and its heat capacity and electrical resistivity are measured at elevated temperatures.

Из оксидов хрома, гадолиния и карбоната кальция твердофазным способом синтезирован хромит GdCaCr 2O 5.5. Методом рентгенофазового анализа определено, что соединение кристаллизуется в тетрагональной сингонии со следующими параметрами решетки: a = 10.77 А; с = 15.84 А; V° = 183.3 А 3; Z = 16, V° эл.яч = 11.8 A 3; ρ рент = 5.63; ρ пикн = 5.55 ± 0.05 г/см 3. С помощью калориметра ИТ-С-400 в интервале температур 298.15-673 К была измерена теплоемкость соединения. При 448 и 473 K на кривой теплоемкости наблюдаются резкие аномальные скачки, связанные, вероятно, с фазовыми переходами второго рода. Выведены уравнения, описывающие зависимость С p° ~ f (T), вычислены функции С° p (T), S°(T), H°(T)-H°(298.15) и Ф xx(Т) хромита в интервале 298.15-673 К. Проведено исследование зависимостей диэлектрической проницаемости и электросопротивления соединения от температуры в диапазоне 303-383 К, которое показало, что исследуемый хромит обладает полупроводниковыми характеристиками.

Chromite GdSrCr2O5.5 was synthesized from the corresponding oxides and carbonates. X-ray powder diffraction analysis showed that the compound forms tetragonal crystals: a = 10.79 Angstrom, c = 16.72 Angstrom, V = 1946.6 Angstrom(3), V(unit cell)degrees = 121.7 Angstrom(3), Z = 16; rho(X-ray) = 5.96 g/cm(3), rho(pycn) = 5.91 +/- 0.07 g/cm(3). The heat capacity of the chromite was measured in the temperature range 298.15-673 K, and abrupt anomalous jumps were observed at 348, 398, 448, and 548 K, probably related to second-order phase transitions. Equations describing the dependence C(p)degrees similar to f(T) were derived, and the chromite functions C(p)degrees(T), Sdegrees(T), Hdegrees(T) - Hdegrees(298.15), and Phi(xx)(T) were calculated for the temperature range 298.15-673 K. The temperature dependence of the chromite dielectric constant was studied; it was found that the chromite has a high dielectric constant and some features that agree well with thermochemical data in the range 298.15-673 K.

Manganites LaCsMMn2O6 (M = W Ca, Sr, Ba) have been synthesized by a solid-state technique from oxides and carbonates. Their crystal systems and unit cell parameters have been deten-nined by X-ray powder diffraction. LaCsMgMn2O6 is tetragonal, a = 11.06 Angstrom, c = 22.07 Angstrom, V = 2699.7 Angstrom(3), V-un.cell = 135.0 Angstrom(3), Z = 20, rho(X-ray) = 6.17 g/cm(3), rho(pycn) = 6.14 +/- 0.03 g/cm(3). The LaCsCaMn2O6 is cubic, a = 10.80 Angstrom, V = 1259.7 Angstrom(3), V-un.cell = 125.97 Angstrom(3), Z = 10, rho(X-ray) = 7.35 g/cm(3), rho(pycn) = 7.31 +/- 0.03 g/cm(3). LaCsSrMn2O6 is cubic, a = 10.89 Angstrom, V = 1291.46 Angstrom(3), V-un.cell = 129.146 Angstrom(3), Z = 10, rho(X-ray) = 7.27 g/cm(3), rho(pycn) = 7.25 +/- 0.04 g/cm(3). LaCsBaMn2O6 is tetragonal, a = 11.04 Angstrom, c = 16.98 Angstrom, V = 2069.6 Angstrom(3), V-un.cell = 129.4 Angstrom(3), Z = 16, rho(X-ray) = 7.89 g/cm(3), rho(pycn) = 7.81 +/- 0.07 g/cm(3). The heat capacities of the above phases have been investigated using dynamic calorimetry in a temperature range of 298.15-673 K. Second-order phase transitions have been found in the LaCsMgMn2O6 (448 K) and LaCsSrMn2O6 (498 K). The C(p)degrees similar tof(T) equations and thermodynamic functions C(p)degrees (T), Hdegrees(T) - Hdegrees(298.15), Sdegrees(T), and Phi(T) have been calculated for the range of 298.15-673 K.