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  • Author or Editor: V. Parvanova x
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Abstract  

TG, DTA and DSC curves of Cd2[Ti2(O2)2O(OH)6]·H2O were recorded and used to determine the isothermal conditions suitable for obtaining the intermediate samples corresponding to the phases observed during the thermal decomposition. The samples were identified by quantitative analysis, IR spectroscopy and X-ray analysis. The experimental results were used to propose a mechanism of thermal decomposition of the investigated compound to CdTiO3. The optimum conditions were also determined for obtaining CdTiO3 with well-defined crystallinity.

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Abstract  

Bi-peroxotitanate was synthesized by a peroxo method and after thermal decomposition Bi2Ti2O7 was obtained. DTA, TG and DSC curves of Bi2[Ti2(O2)4(OH)6]5H2O were recorded and used to determine isothermal conditions suitable for obtaining the intermediate samples corresponding to the phases observed during the thermal decomposition. The samples were identified by quantitative analysis, IR spectroscopy and X-ray analysis. The experimental results were used to propose a mechanism of thermal decomposition of the investigated compound to a nanosized Bi2Ti2O7. The optimum conditions were also determined for obtaining Bi2Ti2O7, which is applicable for piezosensors.

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Abstract  

Potassium peroxotitanate was synthesized by the peroxo method. During the thermal decomposition K2Ti2O5 can be obtained. The isothermal conditions for decomposition of K2[Ti2(O2)2(OH)6]3H2O were determined on the base of DTA, TG and DSC results. DTA and TG curves were recorded in the temperature range 20 and 900C at a heating rate of 10C min–1. The obtained intermediate compounds were characterized by means of quantitative analysis and IR spectroscopy. The mechanism of thermal decomposition of K2[Ti2(O2)2(OH)6]3H2O to K2Ti2O5 was studied. The optimal conditions for obtaining K2Ti2O5 were determined (770C for 10 h).

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Abstract  

Methods of DTA, TG, X-ray phase analysis and IR spectroscopy were used to study the thermal dehydration and decomposition of Ni2+ and Zn2+ peroxotitanates to the corresponding metatitanates. The course of the process was established and the intermediate phases were identified. The information obtained was utilized to determine the optimum temperatures of heating the initial peroxotitanates for conversion to metatitanates with a fairly high degree of crystallinity (for ZnTiO3 the optimum temperature is 600C, while for NiTiO3 it is 550C).

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Abstract  

Methods of DTA, TG, DSC, IR spectroscopy and X-ray phase analysis were used to study the thermal dehydration and decomposition of Ca2+ and Sr2+ peroxotitanates to the corresponding metatitanates. The stages of the process and the intermediate phases were identified. The information obtained was utilised to determine the optimum temperatures of heating of the initial peroxotitanates to yield metatitanates with a fairly high degree of crystallinity (for CaTiO3 680C, and for SrTiO3 650C).

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Abstract  

The state diagrams (T-x) of the systems Ag2Te-ZnTe(I) and Ag2Te-Zn(II) are offered on the ground of data obtained by differential thermal analysis, X-ray phase analysis, microstructural analysis and measurements of the density and the microhardness of samples synthesized. The systems studied are quasibinary sections of the ternary system Ag-Zn-Te. System I is characterized by two eutectic and three eutectoidal non-variant equilibria as well as by an intermediate compound Ag2ZnTe2, which melts congruently at 880C. The latter exists in the range from 120 to 880C in two polymorphic modifications (Tʅ→β=515C). System II is characterized by one eutectic, two eutectoidal and one peritectic nonvariant equilibria, boundary solid solutions on the ground of Ag2Te and Zn and one intermediate phase of the composition Ag4Zn3Te2, which melts congruently at 880C.

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Abstract  

The phase diagram of the system Ag4SSe-SnTe is studied by means of X-ray diffraction, differential thermal and metallographic analyses and measurements of the microhardness and the density of the material. This diagram is divided into two eutectic-type subdiagrams by the composition Ag4SSe·2SnTe. The unit-cell parameters of the intermediate phases 3Ag4SSe·SnTe (phase A) and -Ag4SSe·2SnTe (phase B) are determined as follows: for phase A: a=0.7851 nm, b=0.7196 nm, c=0.6296 nm, =101.32°, =85.90°, =111.36°; for phase B: a=0.3662 nm, b=0.3303 nm, c=0.3343 nm, =90.74°, =108.94°, =91.91°. The phase Ag4SSe·2SnTe melts congruently at 615°C and a polymorphic transition of the phase takes place at T - =110°C.

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Abstract  

The phase diagram of the system CdI2-Bi2O3 is studied by means of X-ray diffraction, differential thermal analysis and measurements of the density of the material. As a result of the synthetic and peritectic interactions, two incongruently melting intermediate phases i.e. phase A - CdI22Bi2O3 and phase B - CdI24Bi2O3 (stable in the temperature interval 370-850C) are formed. The phase A exists in two polymorphic forms with a temperature of the phase transition T a b=320-370C. The unit cell parameters at low temperature modification of a-CdI22Bi2O3 were determined. (a=1.032 nm, b=1.046 nm, c=1.046 nm, α=115.02, β=109.11 and γ=82.04). The phases A and B have fields of homogeneity.

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Abstract  

The phase diagram of the system Ag4SSe–As2Se3 is studied by means of X-ray diffraction, differential thermal analyses and measurements of the microhardness and the density of the materials. The unit-cell parameters of the intermediate phases 3Ag4SSeAs2Se3 (phase A) and Ag4SSe2As2Se3 (phase B) are determined as follows for phase A: a=4.495 , b=3.990 , c=4.042 , α=89.05, β=108.98, γ=92.93; for phase B: a=4.463 , b=4.136 , c=3.752 , α=118.60, β=104.46, γ=83.14. The phase 3Ag4SSeAs2Se3 and Ag4SSe2As2Se3 have a polymorphic transition α↔β consequently at 105 and 120C. The phase A melts incongruently at 390C and phase B congruently at the same temperature.

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