High-Temperature interaction between calcium and strontium titanodisilicates

Abstract

High-temperature interactions between the calcium and strontium titanodisilicates were studied. It was determined that two limited series of solid solutions in the tetragonal system based on these initial compounds are formed. It was found that the changes in the physical-chemical properties of the solid solutions are discontinuous functions of solution composition. Glasses and glass ceramic materials based on the experimental system Ca 2 TiSi 2 O 8 -Sr 2 TiSi 2 O 8 were obtained and the characteristic features of the crystallization of glass and the temperature range of the existence of the crystalline phase were determined.It is known that glasses and glass ceramic materials based on titanosilicates of alkali-earth metals are used successfully in the production of different glasses, glazes, enamels, and pyroceramics. In this connection the purposeful synthesis and production of these materials can be accomplished only on the basis of a complete understanding of the physical-chemical processes occurring during the reactions in the solid state and crystallization of glasses and metals.The published information on the reactions leading to the formation of ternary compounds of titanosilicates of alkaliearth metals is limited, and there is no published information on the kinetics and mechanisms of the formation of such compounds. Essentially, the studies are concerned only with obtaining calcium, barium, and strontium titanosilicates and not with the complex processes associated with the formation and recrystallization of stable phases [1 -4].To work out rational regimes for the synthesis of titanosilicates of alkali-earth metals it is necessary to study the process leading to their formation in a wide temperature range.This article presents the results of an investigation of the high-temperature chemical interaction between calcium titanodisilicates (Ca 2 TiSi 2 O 8 ) and strontium titanodisilicates (Sr 2 TiSi 2 O 8 ). The system Ca 2 TiSi 2 O 8 -Sr 2 TiSi 2 O 8 was studied by means of x-ray diffraction, crystal-optics, IR-spectroscopic, and electron-microscopic analyses.6The compounds Ca 2 TiSi 2 O 8 and Sr 2 TiSi 2 O 8 synthesized from oxide compounds by the solid-phase method of sintering served as the initial materials for synthesizing the solid solutions.The crystal-optical studies performed by the immersion method [5] using a MIN-8 microscope showed that the refractive indices of the crystals are as follows: N g = 2.051, N p = 1.962 for Ca 2 TiSi 2 O 8 ; N g = 1.764, N p = 1.730 for Sr 2 TiSi 2 O 8 ; density at 20°C 3110 kg/m 3 for Ca 2 TiSi 2 O 8 and 3723 kg/m 3 for Sr 2 TiSi 2 O 8 .X-ray diffraction analysis showed that both compounds -calcium titanodisilicate and strontium titanodisilicate, forming the binary system Ca 2 TiSi 2 O 8 -Sr 2 TiSi 2 O 8 , are isostructural and crystallize in the tetragonal system with the following unit-cell parameters: a = 0.838 nm, c = 0.534 nm for Ca 2 TiSi 2 O 8 and a = 0.852 nm, c = 0.493 nm for Sr 2 TiSi 2 O 8 .According to the notions of isomorphism of crystalchemical st...

Review on silicate and borosilicate‐based glass sealants and their interaction with components of solid oxide fuel cell

“…Many works are reported regarding glasses with SrO for sealant application in the SOFC 179–192 However, its high contents may create some limitations as sealing material 183 . In a glass system, the role of SrO depends on initial composition; mostly, it acts as a modifier in the glass.…”

“…In addition, all sealing couples show good joining after being held at 750 C for 1000 hours. 178 SrO-containing glass sealant Many works are reported regarding glasses with SrO for sealant application in the SOFC [179][180][181][182][183][184][185][186][187][188][189][190][191][192] However, its high contents may create some limitations as sealing material. 183 In a glass system, the role of SrO depends on initial composition; mostly, it acts as a modifier in the glass.…”

Influence of SrO content on microstructure and crystallization of glazes in the SiO2–Al2O3–CaO–MgO–K2O system

“…In the next work, glass-crystalline material was obtained in the BaO/SrO-MgO-B 2 O 3 -SiO 2 system at SrO content of 40.4 mass%, in which the crystalline phases Sr 2 MgSi 2 O 7 and SrB 2 Si 2 O 8 were present [30]. There are a number of works regarding glasses with SrO for applications in various areas [31][32][33][34][35][36][37]; however, its high content in these glass systems, the purpose and time of work at the target conditions, create some limitations in the possibilities of their application as a material for frits and ultimately glazes.…”