Search

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]

Sequential annealing of stoichiometric mixtures of CaCO3, Pr6O11(Nd2O3), and GeO2 in air at 1423–1473 K yields germanates CaPr2Ge3O10 and CaNd2Ge3O10. Their crystal structure is refined via X-ray diffraction. The high-temperature heat capacity (320–1000 K) is measured by means of differential scanning calorimetry. The thermodynamic properties of germanates are calculated using experimental dependences Cp = f(T). [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]

Copper samarium germanate CuSm2Ge2O8 have been synthesized by the ceramic method from CuO, Sm2O3, and GeO2 in air at the final calcination temperature 1273 K (200 h), and its crystal structure has been determined (space group Cm; a = 9.7592(2) Å, b = 15.2608(4) Å, c = 8.2502(2) Å, β = 148.2566(8)°, V = 646.46(3) Å3). The temperature dependence of the molar heat capacity Cp= f(T) measured in the temperature range 350–1000 K shows a maximum at Tmax = 498.5 K caused by the phase transition. Thermodynamic properties have been calculated from experimental data. [ABSTRACT FROM AUTHOR]

Pb10 –xEux(GeO4)2 +x(VO4)4 –x (x = 0.1, 0.2, 0.3) Eu-substituted lead germanatovanadates with the apatite structure have been prepared by solid-state reactions, via firing in air in the temperature range 773–1073 K, using oxides (PbO, Eu2O3, GeO2, and V2O5) as starting materials. Using X-ray diffraction, we have determined the hexagonal cell parameters (sp. gr. P63/m) of the synthesized phases and refined their crystal structure (the atomic position coordinates, isotropic thermal parameters, and principal bond lengths in their structure are presented). We have measured the luminescence spectra of the Pb10 –xEux(GeO4)2 +x(VO4)4 –x (x = 0.1, 0.2, 0.3) apatites and shown that europium concentration has little effect on the shape of the luminescence spectra. Using experimental heat capacity data obtained for polycrystalline samples by differential scanning calorimetry in the temperature range 350–1050 K, we calculated the main thermodynamic functions of the Eu-substituted lead germanatovanadates. [ABSTRACT FROM AUTHOR]

Bi4–xPrxTi3O12 (x = 0.4, 0.8, 1.2, 1.6) solid solutions have been prepared by solid-state reactions, via multistep firing of stoichiometric mixtures of their constituent oxides in air at temperatures from 1003 to 1323 K. Their crystal structure has been determined using X-ray diffraction, and their luminescence spectra have been measured at room temperature. High-temperature heat capacity of polycrystalline substituted bismuth titanate samples has been determined by differential scanning calorimetry. The Cp(T) curves of the solid solutions with x = 0.4 and 0.8 have extrema related to phase transitions. Experimental data have been used to calculate the main thermodynamic functions of the solid solutions. [ABSTRACT FROM AUTHOR]