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Abstract  

A new type of glass from the Na2O–MeO–Al2O3–SiO2–LaF3 system where MeO = MgO, CaO, BaO and SrO has been studied. The aim of the investigation was to determine, by means of thermal techniques (DTA and DSC), the influence of alkaline earth ions additions on its thermal stability and the ability of LaF3 phase to crystallization. The effect of LaF3 crystallization was analyzed in connection with glass composition expressed by the Al2O3/(MeO + Na2O + 3La2F6) ratio varying from 0.4 to 0.8 for the alkaline earth admixtures. The compositions of the glasses have been designed so as to make it possible to define the effect of the charge of the ion modifiers (Na+, Me2+, La3+) on the alumina position in the framework of the glass. Two series of glasses were obtained with a different F content. The formation of LaF3 depends directly on the strength of the network and can be control by the Al2O3/modifiers ratio as well as the content of fluorine ions. Generally, it can be stated that transparent glass-ceramic with nanocrystallization of LaF3 can be obtained for Al2O3/(Na2O + MeO + 3La2F6) ≤0.6 in the examined glasses. The more the ionicity of the alkaline earth ions the greater the tendency for the crystallization of Me2LaF7 and MeF2. In the glass structure the substitution of oxygen ions by F ions facilitated the crystallization of LaF3. Simultaneously, it influenced the thermal stability of the aluminosilicate network and induced the crystallization of appropriate silicates during the heat treatment.

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Abstract  

Glasses have been synthesized in the system SiO2–Al2O3–Na2O–AlF3–LaF3–Er2O3. A base glass (in mol% 67SiO2–9Al2O3–20Na2O–Al2F6–3La2F6) was modified by 0.5, 0.75, 1, 1.25, 1.5, 2 and 5 mol% Er2O3, respectively. Glasses were prepared by conventional fusion method from 20 g batches. The glass transition temperature (T g), the jump-like changes of the specific heat (ΔC p) accompanying the glass transition and the enthalpy of crystallization (ΔH) were calculated. DTA measurements clearly reveal that the increase of the Er2O3 content in the glass changes the effects of crystallization and diminishes the thermal stability of the glassy network. In the same time the changes in the transition temperature are observed. The formation of NaLaF4 and Na1.45La9.31(SiO4)6(F0.9O1.1) as a main phase was confirmed. The diminishing of the thermal stability was connected with erbium which incorporated into Na1.45La9.31(SiO4)6(F0.9O1.1) structure.

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Abstract  

Oxyfluoride glass-ceramics based on the aluminosilicate glass-matrix with the nano-phase of fluoride is an interesting material for optoelectronics. A new glass from the SiO2–B2O3–Na2O–LaF3 system in which nanocrystallization of LaF3 could be obtained as well is presented. Thermal stability of glass and the crystalline phases formed upon heat treatment were determined by DTA/DSC and XRD methods, respectively. The effect of the glass composition on thermal stability was investigated by the SEM method. It has been found that the addition of LaF3 increases the tendency to decomposition of the borosilicate glass. In glasses with the ratio B2O3/(Na2O+3La2F6)<1 it is possible to obtain the immersed crystallization of LaF3 in transparent glassy matrix. The process is preceded by LaOF formation. Glasses with the composition B2O3/(Na2O+3La2F6)≥1 revealed the tendency to La(BSiO5) crystallization.

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Abstract  

New oxyfluoride glasses based on the system ZrO2-Pr2O3-ZrF4-BaF2 were obtained, and the glass forming ability of this system was evaluated. The effects of glass composition on both thermal stability and the crystalline phases formed upon heat treatment were determined by the DSC and XRD methods, respectively. The composition with higher thermal stability and better glass forming ability contained 2 mol% of oxides.

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Abstract  

The influence of fluorine content on the structure and crystallization of oxyfluoride glasses from the Na2O–Al2O3–SiO2–LaF3 system was studied by DTA/DSC, XRD, FTIR and SEM methods. It has been found that the increase in the fluorine content in the structure of oxyfluoride glasses causes the increase of the flexibility of their structure, which inhibits the process of crystallization of the silicate- aluminium matrix. Simultaneously the ability of the glass for LaF3 crystallization, which shows a multistage character, is increasing. Analysis of the local atomic interactions in the structure of glasses has been used to explain the course of the crystallization.

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.08.002 . 5. Środa , M 2009 Effect of Er 2 O 3 on thermal stability of oxyfluoride glass . J Therm Anal Calorim 97 : 239 – 243 10.1007/s10973-009-0257-3 . 6

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Effect of Er 2 O 3 on thermal stability of oxyfluoride glass . J Therm Anal Calorim 2009 97 : 239 – 243 10.1007/s10973-009-0257-3 . 14. Ito , A , Tanaka , K , Kawaji , H , Atake , T

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. 8. Sroda , M , Wacławska , I , Stoch , L , Reben , M 2004 DTA/DTS study of nanocrystallization in oxyfluoride glass . J Therm Anal Calorim 77 : 193 – 2000 10.1023/B:JTAN.0000033203.95251.d6

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