Search

Pb10 –xPrx(GeO4)2 +x(VO4)4– x (x = 0, 1, 2, 3) apatites have been prepared by solid-state reactions via sequential firing of appropriate oxide mixtures (PbO, Pr2O3, GeO2, and V2O5) in air in the temperature range 773–1073 K. Their unit-cell parameters have been determined as functions of temperature by high-temperature X-ray diffraction measurements, and the linear and volume expansion coefficients of Pb7Pr3(GeO4)5(VO4) have been calculated. The heat capacity of the synthesized Pb10 –xPrx(GeO4)2 +x(VO4)4– x (x = 0, 1, 2, 3) compounds with the apatite structure has been determined by differential scanning calorimetry in the temperature range 350–1050 K. The cp(T) curves of the samples with x = 1, 2, and 3 have been shown to have extrema (in particular, peaks at 701, 917, and 1018 K for the x = 3 sample) due to phase transitions. The experimental Cp(T) heat capacity data have been used to evaluate the thermodynamic functions of the synthesized apatites. [ABSTRACT FROM AUTHOR]

Dense silicon carbide-based ceramic composites reinforced with SiCf fiber have been produced by hot pressing at a temperature of 1850°C. The reinforcing agent used was silicon carbide fiber produced by siliciding carbon cloth with SiO vapor. It has been shown that raising fiber content from 1 to 7 wt % increases the density, bending strength, and fracture toughness of the material, which reach ρ = 3.20 ± 0.01 g/cm3, δb = 450 ± 26 MPa, KIс = 5.6 ± 0.1 MPa m1/2 at 7 wt % SiC fiber. [ABSTRACT FROM AUTHOR]

The RxBi2– xGeO5 (R = Sm–Yb, Y) and BiGeO5 (R1 = Y, R2 = Pr, Nd) germanates have been prepared by solid-state reactions, by sequential firing of oxide mixtures in air in the temperature range 1003–1223 K. Their heat capacity has been determined by differential scanning calorimetry. The Cp(T) data have been shown to be well represented by the classic Maier–Kelley equation in the range 350–1000 K. [ABSTRACT FROM AUTHOR]

The PrFeGe2O7 and NdFeGe2O7 germanates have been prepared by solid-state reactions using stoichiometric mixtures of Pr2O3 (Nd2O3), Fe2O3, and GeO2 as starting oxides, which were sequentially fired between 1273 and 1473 K in air, and their high-temperature heat capacity has been determined by differential scanning calorimetry. The experimental Cp(T) data obtained have been used to evaluate their thermodynamic properties. [ABSTRACT FROM AUTHOR]

The Bi12TiO20, Bi4Ti3O12, and Bi2Ti4O11 bismuth titanates have been prepared by solid-state reactions, via multistep firing of stoichiometric mixtures of their constituent oxides in air at temperatures from 1003 to 1273 K (Bi12TiO20, to 1123 K). The heat capacity of polycrystalline samples of the synthesized compounds has been determined by differential scanning calorimetry in the temperature range 330–1050 K. The Cp(T) curves of Bi4Ti3O12 and Bi2Ti4O11 show peaks at temperatures of 943 and 509 K, respectively, due to ferroelectric phase transitions. The experimental data have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy change of the bismuth titanates. [ABSTRACT FROM AUTHOR]

The R2Ge2O7 (R = Pr–Lu, Y) rare-earth germanates have been prepared by solid-state reactions by firing stoichiometric R2O3 + GeO2 mixtures in air at temperatures in the range 1273–1473 K. The unit-cell parameters (a, c, and V) of the R2Ge2O7 (R = Tb–Lu) compounds have been shown to be linear functions of the ionic radius of the rare-earth elements. The high-temperature heat capacity of polycrystalline samples of the germanates has been determined by differential scanning calorimetry in the temperature range 350–1000 K. The variation in the specific heat of R2Ge2O7 has been shown to be correlated with the dependence of the heat capacity of rare-earth oxides on the ionic radius of the rare-earth element within each tetrad. [ABSTRACT FROM AUTHOR]

Pb10 –xLax(GeO4)2 +x(VO4)4 –x (x = 0, 1, 3) compounds with the apatite structure have been prepared by solid-state reactions via multistep firing of appropriate oxide mixtures in air in the temperature range 773–1073 K. The heat capacity of the synthesized polycrystalline samples has been determined by differential scanning calorimetry. The experimental Cp(T) data have been used to evaluate the thermodynamic properties of the lead lanthanum germanatovanadates: enthalpy increment, entropy change, and reduced Gibbs energy. [ABSTRACT FROM AUTHOR]

Abstract—: Polycrystalline In2Ge2O7 and YInGe2O7 samples have been prepared by solid-state reactions, by sequentially firing stoichiometric mixtures of In2O3, Y2O3, and GeO2 at temperatures from 1273 to 1473 K. The molar heat capacity of the indium and yttrium indium pyrogermanates has been determined by differential scanning calorimetry in the range 320-1000 K. The experimental Cp(T) data have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy of In2Ge2O7 and YInGe2O7. [ABSTRACT FROM AUTHOR]

Abstract—: This paper presents dilatometric analysis data for the sintering of off-the-shelf molybdenum disilicide (MoSi2) powder prepared by magnesiothermic synthesis. We have obtained continuous shrinkage curves for MoSi2 powder compacts with an initial relative density of 70% at different heating rates: 5, 10, 20, and 30°C/min. From a quantitative analysis of densification curves for the compacts, the activation energy for the initial stage of sintering has been determined to be Q = 695 kJ/mol. It has been shown that the dominant process in the initial stage of MoSi2 powder sintering is volume diffusion from grain boundaries and surfaces. [ABSTRACT FROM AUTHOR]

Polycrystalline HoBiGeO5 and ErBiGeO5 samples have been prepared by solid-state reactions, by firing stoichiometric mixtures of Ho2O3 (Er2O3), Bi2O3, and GeO2. The effect of temperature on the heat capacity of the synthesized compounds has been investigated by differential scanning calorimetry in the range 350-1000 K. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of bismuth holmium and bismuth erbium germanates: enthalpy increment, entropy change, and reduced Gibbs energy. [ABSTRACT FROM AUTHOR]

Neodymium dititanate, Nd2Ti2O7 (monoclinic structure, sp. gr. P21), has been prepared by solid-state reaction in air at temperatures from 1673 to 1773 K using the Nd2O3 and TiO2 oxides as starting materials. The high-temperature heat capacity of the resultant polycrystalline Nd2Ti2O7 samples has been determined by differential scanning calorimetry. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of neodymium dititanate (enthalpy increment H°(T)-H°(320 K), entropy change S°(T)-S°(320 K), and reduced Gibbs energy Ф°(T)) in the temperature range 320-1053 K. [ABSTRACT FROM AUTHOR]

The Pb8La2(GeO4)4(VO4)2 and Pb8Nd2(GeO4)4(VO4)2 germanatovanadates with the apatite structure have been prepared by solid-state reactions, by sequentially firing stoichiometric mixtures of PbO, La2O3 (Nd2O3), GeO2, and V2O5 in air at temperatures of 773, 873, 973, and 1073 K. The effect of temperature on the heat capacity of the resultant polycrystalline samples has been studied by differential scanning calorimetry at temperatures from 350 to 950 K using polycrystalline samples. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of the lead lanthanum and lead neodymium germanatovanadates. [ABSTRACT FROM AUTHOR]

Polycrystalline TbBiGeO and DyBiGeO samples have been prepared by solid-state reactions, by firing stoichiometric mixtures of TbO (DyO), BiO, and GeO in air at 1003, 1073, 1123, 1143, 1173, and 1223 K. The molar heat capacity of the bismuth terbium and bismuth dysprosium germanates has been determined by differential scanning calorimetry. The experimental C ( T) data obtained in the range 350-1000 K have been used to evaluate the thermodynamic functions of the synthesized oxide compounds: enthalpy increment, entropy change, and reduced Gibbs energy. [ABSTRACT FROM AUTHOR]

RSnO (R = Pr-Lu) rare-earth stannates with the pyrochlore structure have been synthesized by solid-state reactions, by firing stoichiometric mixtures of SnO and RO in air at 1473 K. The high-temperature heat capacity of the rare-earth stannates has been determined by differential scanning calorimetry in the temperature range 350 to 1000 K, and the Raman spectra of polycrystalline TbSnO and DySnO samples have been measured. [ABSTRACT FROM AUTHOR]

This paper presents experimental data on the oxidation kinetics of a liquid 65 at % Pb + 35 at % Ge alloy in air. Lead metagermanate, PbGeO, in a glassy state has been prepared by high-temperature oxidation of the melt at 1273 K. Interaction of molten PbGeO with crucible materials (SnO, Au, Pd, and Pt) has been studied by the sessile drop method. Liquid lead germanate has been shown to be highly reactive with substrates from these materials. The heat capacity of the glassy lead metagermanate obtained has been determined by differential scanning calorimetry in the temperature range 300-800 K. In the range 330-630 K, the C( T) data for glassy PbGeO can be represented using the Maier-Kelley equation. Above 630 K, there is a characteristic peak due to glass crystallization processes. [ABSTRACT FROM AUTHOR]

The heat capacity of InVO has been determined by differential scanning calorimetry in the temperature range 339-1089 K. The experimental C( T) data have been used to evaluate the thermodynamic functions of indium orthovanadate: enthalpy increment H°( T)- H°(339 K), entropy change S°( T)- S°(339 K), and reduced Gibbs energy Ф°( Т). The specific heats of GaVO and TlVO have been evaluated. [ABSTRACT FROM AUTHOR]

A method has been proposed for the fabrication of three-dimensional photonic crystals based on ordered opal matrices (OMs), with pores containing iron group metal (M = Ni, Co, Fe) nanoparticles. The core of the method is the reduction of salts and oxides of these metals with supercritical isopropanol. The phase composition of OM/M composites depends on the composition of the starting salts (nitrates or chlorides): the use of ferric chloride leads to the formation of nanoparticles of solid solutions based on nickel metal, α-cobalt, or β-cobalt (Ni-Fe and Co-Fe systems) in opal pores; with the corresponding nitrates, we obtain OM/NiCo (cubic solid solution), OM/Fe, OM/NiFe, OM/NiFe, OM/CoFe, and OM/NiCoFe nanocomposites. We have measured broadband reflection spectra of the (111) surface of the photonic crystals using a fiber-optic technique for taking reflection spectra. The intensity peak in the reflection (band gap) spectrum of the OM/M (M = Fe, Co, Ni) nanocomposites is shown to be shifted to longer wavelengths. [ABSTRACT FROM AUTHOR]

The correlation between the heat capacities of rare-earth cuprates, orthovanadates, and garnets with ionic radius R has been analyzed. It has been shown that the values of C change consistently depending on the radius R within the corresponding tetrads (La-Nd, Pm-Gd, Gd-Ho, Eu-Lu). [ABSTRACT FROM AUTHOR]

Lithium sodium tetragermanate, LiNaGe4O9, has been prepared by solid-state reaction, by sequentially firing stoichiometric mixtures of Li2CO3, Na2CO3, and GeO2 starting materials in air in the temperature range 773–1073 K. Its unit-cell parameters have been determined by X-ray diffraction: a = 4.68007(3) Å, b = 9.3220(8) Å , c = 15.900(2) Å, and V = 694.113 Å (Z = 4, sp. gr. Pcca). The high-temperature heat capacity of the germanate has been determined using differential scanning calorimetry in the temperature range 320–1050 K. The experimental temperature-dependent heat capacity data, Cp(T), have been used to calculate the principal thermodynamic functions of LiNaGe4O9. [ABSTRACT FROM AUTHOR]

The RGaTi2O7 (R = Sm, Ho, Tm, Yb) substituted titanates have been prepared by solid-state reactions, by firing mixtures of the Ga2O3, TiO2, and R2O3 oxides in air at 1273 and 1573 K, and their crystal structure has been determined using X-ray diffraction. The effect of temperature (320–1000 K) on the heat capacity of the synthesized compounds has been studied by differential scanning calorimetry. The experimental Cp(T) data have been used to calculate the principal thermodynamic functions of the titanates. Using the group contribution method, we evaluated the standard enthalpy and Gibbs energy of formation of the RGaTi2O7 (R = Sm, Ho, Tm, Yb) titanates. [ABSTRACT FROM AUTHOR]

Phase relations in the BiO-SnO system have been studied using differential thermal analysis, differential scanning calorimetry, X-ray diffraction, and the sessile drop method. The C( T) curve obtained in the range 350-960 K has a number of extrema, which are attributable to structural changes in BiSnO. The experimental C data have been used to evaluate the thermodynamic properties of the oxide compound. [ABSTRACT FROM AUTHOR]

Thin, ordered TiO · nHO-based films ranging in thickness from tens of nanometers to several microns have been produced by a sol-gel process. Using multilayer deposition from concentrated sols, we have obtained thick coatings that ensure phase contrast with the substrate. Layer-by-layer application of a film-forming sol has been used to produce fiber-optic light delivery devices with a cylindrical irradiator for effective photodynamic therapy, hyperthermia, and laser-induced coagulation of internal organ tissues in the treatment of oncological and nononcological diseases. [ABSTRACT FROM AUTHOR]

The molar heat capacity of SmVO has been determined by differential scanning calorimetry in the temperature range 369-1020 K. The experimental data have been used to evaluate the thermodynamic properties of the oxide compound. The structure of SmVO has been determined at 298 and 973 K. [ABSTRACT FROM AUTHOR]

The molar heat capacity of LuVO has been determined by differential scanning calorimetry in the temperature range 404-908 K. The C( T) curve has been shown to have no extrema. The experimental data have been used to evaluate the thermodynamic functions of lutetium orthovanadate in the temperature range studied. [ABSTRACT FROM AUTHOR]

The heat capacity of ScVO has been determined by differential scanning calorimetry in the temperature range 328-1000 K. The experimental C( T) data have been used to evaluate the thermodynamic functions of scandium orthovanadate: enthalpy increment H( T) - H(328 K) and entropy change S( T) - S(328 K). Data on the temperature effect (30-1000 K) on the heat capacity of ScVO have been systematized. [ABSTRACT FROM AUTHOR]

This review covers some of the main trends in the field of synthesis and the applications of materials based on silicon nitride presented in publications over the past 10-15 years. Attention is paid to the technique for synthesizing nitride and oxynitride compounds and for the production of ceramic construction materials and phosphors in silicon nitride systems. [ABSTRACT FROM AUTHOR]

The heat capacity of PrCuO has been determined by differential scanning calorimetry in the temperature range 364-1064 K. The experimental C( T) data have been used to evaluate the thermodynamic functions of praseodymium cuprate: enthalpy increment H( T)- H(364 K) and entropy change S( T)- S(364 K). [ABSTRACT FROM AUTHOR]

The heat capacity of InCuO has been determined by differential scanning calorimetry in the temperature range 364-984 K. The C( T) data have been used to evaluate the thermodynamic functions of indium cuprate: enthalpy increment H( T) - H(364 K) and entropy change S( T) − S(364 K). [ABSTRACT FROM AUTHOR]

This paper reports on the results of investigations into the influence of anions (Cl, SO,NO), which stabilize the sol-gel synthesis of highly dispersed titanium dioxide, on the crystallization and phase transition of TiO upon dehydration. The effect of the size factor on the phase composition of TiO in SiO/TiO nanocomposites has been investigated using a three-dimensional opal matrix as a set of nanoreactors for the sol-gel synthesis of TiO · nHO. It has been shown that there is a possibility of extending the region of the existence of a thermodynamically metastable modification of TiO (anatase) to the temperature of 1100°C due to the changes in the conditions of the sol-gel synthesis of TiO · nHO. [ABSTRACT FROM AUTHOR]

We have studied the influence of SHS aluminum nitride content (5-15%) and particle size on the fabrication conditions (hot pressing in a nitrogen atmosphere) of SiN-based ceramics containing CaO-AlO-AlN sintering aids. The results demonstrate that the reaction of SiN with a eutectic calcium aluminate mixture during liquid-phase sintering leads to the formation of α-sialon-based intergranular phases: CaSiAlON. The addition of AlN to starting mixtures contributes to a more complete conversion of the calcium aluminate sintering aid to Ca-α-sialon and influences the relationship between α-SiN and β-SiN in the ceramics. We examine the influence of synthesis conditions and the percentages of added calcium aluminates and aluminum nitride on the density, porosity, and bending strength of the ceramics. Thermogravimetric analysis data demonstrates that the SiN + Ca-α-sialon composites obtained are stable to oxidation in air up to 1300°C. [ABSTRACT FROM AUTHOR]

SiN/TiN composites have been produced by hot pressing at temperatures from 1600 to 1800°C in a nitrogen atmosphere, using silicon nitride powders prepared by self-propagating high-temperature synthesis and surface-modified with titanium dioxide nanoparticles. We examined the effect of TiO content on the microstructure, phase composition, and mechanical strength of the ceramics. It is shown that titanium nitride can be formed by the reaction SiN + TiO → TiN + NO + NO + 3Si. The SiN/TiN composites containing 5-20% TiN have a low density, high porosity, and a bending strength of 60 MPa or lower. In SiN/TiN ceramics produced using calcium aluminates as sintering aids, the silicon nitride grains are densely packed, which ensures an increase in strength to 650 MPa. [ABSTRACT FROM AUTHOR]

Using solid-state reactions and a combination of carbothermal reduction-nitridation with solgel processing, we have synthesized a number of oxynitride phases: Eu-doped Ca-sialons. We have measured the pulsed cathodoluminescence spectra of the synthesized powders under pulsed electron beam excitation and determined their emission parameters, including temporal emission characteristics. [ABSTRACT FROM AUTHOR]

The CaSm2Ge3O10 germanate has been prepared by firing stoichiometric mixtures of CaCO3, Sm2O3, and GeO2 in air in the temperature range 1423–1473 K. X-ray powder diffraction characterization with the use of the derivative difference minimization method has shown that CaSm2Ge3O10 has a monoclinic structure (sp. gr. P21/c, 293 К) with unit-cell parameters a = 6.9779(8) Å, b = 6.92859(7) Å, c = 18.8907(2) Å, and β = 108.3280(8)°. The high-temperature heat capacity of calcium samarium germanate samples has been determined in the temperature range 320–1000 K by differential scanning calorimetry and the experimental Cp(T) data have been used to evaluate thermodynamic properties of CaSm2Ge3O10. [ABSTRACT FROM AUTHOR]

NiCo solid solutions and Ni-Cu bimetallic particles have been prepared in opal-matrix nanocomposites by reacting Ni, Co, and Cu double salts and oxides with supercritical (SC) isopropanol. According to X-ray diffraction and transmission electron microscopy data, the nanocomposites have an X-ray amorphous opal matrix and contain crystalline nanoparticles of individual metals, solid solutions, or bimetallic materials of various morphologies in the opal pores. Mesoporous silica gel matrix composites remain X-ray amorphous after treatment in SC alcohols because of the small particle size of the metallic phase, or form solid solutions between Ni and Co silicates. The phase composition of the composites can be controlled by varying experimental conditions. [ABSTRACT FROM AUTHOR]

Three-dimensional nanocomposites consisting of an opal matrix and a metal have been prepared by the interaction of salts and oxides of different elements (Ni, Co, Fe, etc.) embedded in an opal matrix with isopropanol in the range of supercritical state parameters of the alcohol. According to X-ray powder diffraction analysis and transmission electron microscopy data, the composites consist of an X-ray amorphous opal matrix with pores filled by nanoparticles of Co (or CoO), metallic Ni, or FeO with a magnetite structure of various morphology. The sizes of the nanoparticles do not exceed the diameter of the pores in the opal matrix. A complex investigation of the nanocomposites has been performed using the electron magnetic resonance and vibrating magnetometry methods. All the studied samples at room temperature exhibit a ferromagnetic behavior. The coercive force of the samples lies in the range from 150 Oe for iron-containing nanocomposites to 565 Oe for cobalt-containing nanocomposites. [ABSTRACT FROM AUTHOR]

Silicon-nitride-based ceramics containing AlO-CaO sintering aids and reinforced with silicon carbide whiskers have been prepared by hot pressing at 1650°C in a nitrogen atmosphere, and their microstructure, phase composition, and mechanical properties have been studied. The results indicate that the SiN ceramic containing 15 wt % calcium aluminate additions and 10 wt % SiC fibers has a dense microstructure with a uniform distribution of skeletal and dendritic silicon carbide crystals. The observed variations in the morphology of the crystals are tentatively attributed to the secondary crystallization of silicon carbide from the eutectic calcium aluminate melt during cooling. [ABSTRACT FROM AUTHOR]

Silicon nitride ceramics containing calcium aluminates as sintering aids have been prepared by hot pressing at 1650°C in a nitrogen atmosphere, and the effect of sintering aid content on their microstructure, phase composition, mechanical strength, and air oxidation resistance has been studied. The results demonstrate that the Si3N4 ceramic containing 10 wt % calcium aluminates has a uniform distribution of intergranular multicomponent oxide phases and consists of densely packed silicon nitride grains. Owing to this, it offers the maximum mechanical strength (850 MPa) and is stable to air oxidation up to 1300°C. [ABSTRACT FROM AUTHOR]

We have studied the effect of the size factor on the phase composition of fine-particle TiO2 using three-dimensional opal crystals as a system of nanoreactors for sol-gel synthesis of TiO2 · nH2O. The results indicate that the stability region of the thermodynamically metastable TiO2 polymorphs can be extended to higher temperatures. [ABSTRACT FROM AUTHOR]

Silicon carbide whiskers have been prepared by sintering silicon nitride powder in a graphite reactor at 1800°C under a nitrogen atmosphere. The whiskers differ in morphology: tubular needles, hollow faceted fibers with a square cross section, and solid fibers with a triangular cross section. The average diameter of the needles is 0.5−5 μm, and that of the faceted fibers is up to 20 μm. The fibers range in length up to several millimeters. Such silicon carbide whiskers can be used as reinforcing agents for structural ceramics based on nonoxide materials. [ABSTRACT FROM AUTHOR]

Silicon nitride nanofilaments were synthesized at 1600°C in nitrogen on the surface of a ceramic substrate made of amorphous silicon oxynitride obtained by hexamethyl disilasane pyrolysis. The diameter of filaments represented by different morphological types (filaments, ribbons, needles) was 100–500 nm, and the length was several millimeters. [ABSTRACT FROM AUTHOR]

Bi, Te, and Bi2Te3 nanoparticles have been prepared by reducing bismuth salts, telluric acid, and their decomposition products with supercritical isopropanol in opal pores. [ABSTRACT FROM AUTHOR]

We have studied the reactions between supercritical isopropanol and salts of various elements (silver, copper, gold, zinc, iron, nickel, cobalt, manganese, europium, ruthenium, antimony, bismuth, and tellurium) infiltrated into opal photonic crystals. According to transmission electron microscopy data, the diameter of the SiO2 spheres in the opal crystals is 260 nm, and the nanoparticles of the metals and incomplete reduction products range in size from 2 to 80 nm, i.e., are no greater in size than the opal pores. [ABSTRACT FROM AUTHOR]

Bismuth nanoparticles have been produced in pores of opal matrices by reducing bismuth salts and oxide compounds with supercritical isopropanol. According to transmission electron microscopy data, the diameter of the SiO2 spheres in the opal matrices is about 260 nm, and that of the bismuth nanoparticles does not exceed 80 nm. [ABSTRACT FROM AUTHOR]

The main processes for preparing bulk single crystals and films of photorefractive and piezoelectric Bi12M xO20±δ (M = Group II–VIII elements) sillenite compounds are considered. Experimental data are summarized on the crystal growth of Bi12M xO20±δ from the melt and under hydrothermal conditions, and the key morphological features of sillenites are analyzed. Various types of macroscopic growth defects in sillenite-type crystals are described, and their origin is discussed. The compositions of second-phase inclusions in undoped and doped (Group I–VIII elements) Bi12SiO20, Bi12GeO20, and Bi12TiO20 single crystals are presented, and the main physicochemical properties of various Bi12M xO20±δ crystals are summarized. [ABSTRACT FROM AUTHOR]

The stable and metastable phase equilibria in the Bi2O3–P2O5 system were studied in the range 0–50 mol % P2O5 by differential thermal analysis and x-ray diffraction. The results were used to construct the corresponding phase diagrams. In the equilibrium state, the system contains one sillenite phase with Bi2O3 : P2O5 = 12 : 1 and four other bismuth phosphates (2 : 1, 3 : 1, 5 : 1, and 1 : 1). In a metastable state, resulting from solidification of metastable melts, there exist δ* solid solutions (0–25 mol % P2O5) based on the high-temperature form of Bi2O3 . At lower temperatures, the δ* phase transforms eutectoidally into the metastable δ phase, which has the same structural basis as the high-temperature solid solutions. At room temperature, the δ phase exists in a narrow composition range around 15 mol % P2O5 . At lower P2O5 contents, the δ* phase decomposes at 868 K by a monotectoid reaction to form a mixture of the metastable α and δ phases. The phases 3Bi2O3 · P2O5 (β) and 2Bi2O3 · P2O5 (σ), melting incongruently at 1193 and 1223 K, respectively, appear in both the equilibrium and metastable phase diagrams. [ABSTRACT FROM AUTHOR]

Pb10 –xSmx(GeO4)2 +x(VO4)4 –x (x = 0.2, 0.5, 0.7, 1.0) compounds with the apatite structure have been synthesized by firing appropriate mixtures of the PbO, Sm2O3, GeO2, and V2O5 oxides in air at temperatures from 773 to 1073 K. Their crystal structure has been studied using X-ray diffraction, and their high-temperature heat capacity (350–1000 K) has been determined by differential scanning calorimetry. The data have been used to evaluate their thermodynamic properties. [ABSTRACT FROM AUTHOR]

The molar heat capacity of ScCuO has been determined at temperatures from 350 to 893 K using differential scanning calorimetry. The experimental C( T) data have been used to evaluate the thermodynamic functions of the double oxide. [ABSTRACT FROM AUTHOR]

The CaY2Ge3O10 and CaY2Ge4O12 germanates have been synthesized by a standard ceramic processing route using CaCO3, Y2O3, and GeO2 as starting materials, and their crystal structure has been refined by X-ray diffraction. The high-temperature (350–1000 K) experimental heat capacity data obtained for the germanates by differential scanning calorimetry have been used to calculate their principal thermodynamic functions. [ABSTRACT FROM AUTHOR]