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  • Author or Editor: K. Vosejpková x
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Abstract

Thermal behavior of xGa2O3–(50 − x)PbO–50P2O5 (x = 0, 10, 20, and 30 mol.% Ga2O3) and xGa2O3–(70 − x)PbO–30P2O5 (x = 0, 10, 20, 30, and 40 mol.% Ga2O3) glassy materials were studied by thermo-mechanical analysis (TMA) and differential thermal analysis (DTA). Replacement of PbO for Ga2O3 is accompanied by increasing glass-transition temperature (263 ≤ T g/°C ≤ 535), deformation temperature (363 ≤ T d/°C ≤ 672), crystallization temperature (396 ≤ T c/°C ≤ 640) and decreasing of coefficient of thermal expansion (5.1 ≤ CTE/ppm K−1 ≤ 16.7). Values of Hruby parameter were determined (0.1 ≤ K H ≤ 1.3). The thermal stability of prepared glasses increases with increasing of concentration of Ga2O3.

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Abstract  

DTA was used to study thermal properties and thermal stability of (50-x)Li2O-xTiO2-50P2O5 (x=0–10 mol%) and 45Li2Ot-yTiO2-(55-y)P2O5 (y=5–20 mol%) glasses. The addition of TiO2 to lithium phosphate glasses results in a non-linear increase of glass transition temperature. All prepared glasses crystallize under heating within the temperature range of 400–540°C. The lowest tendency towards crystallization have the glasses with x=7.5 and y=10 mol% TiO2. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were LiPO3, Li4 P2O7, TiP2O7 and NASICON-type LiTi2(PO4)3. DTA results also indicated that the maximum of nucleation rate for 45Li2O-5TiO2-50P2O5 glass is close to the glass transition temperature.

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Abstract  

Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to study the thermal behaviour of (50-x)Na2O-xTiO2-50P2O5 and 45Na2O-yTiO2-(55-y)P2O5 glasses. The addition of TiO2 to the starting glasses (x=0 and y=5 mol% TiO2) resulted in a nonlinear increase of glass transition temperature and dilatation softening temperature, whereas the thermal expansion coefficient decreased. All prepared glasses crystallize under heating within the temperature range of 300–610°C. The contribution of the surface crystallization mechanism over the internal one increases with increasing TiO2 content. With increasing TiO2 content the temperature of maximum nucleation rate is also gradually shifted from a value close to the glass transition temperature towards the crystallization temperature. X-ray diffraction measurements showed that the major compounds formed by glass crystallization were NaPO3, TiP2O7 and NaTi2(PO4)3. The chemical durability of the glasses without titanium oxide is very poor, but with the replacement of Na2O or P2O5 by TiO2, it increases sharply.

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Abstract

The effect of TeO2 additions on the thermal behaviour of zinc borophosphate glasses were studied in the compositional series (100 − x)[0.5ZnO–0.1B2O3–0.4P2O5]–xTeO2 by differential scanning calorimetry, thermodilatometry and heating microscopy thermal analysis. The addition of TeO2 to the starting borophosphate glass resulted in a linear increase of glass transition temperature and dilatometric softening temperature, whereas the thermal expansion coefficient decreased. Most of glasses crystallize under heating within the temperature range of 440–640 °C. The crystallization temperature steeply decreases with increasing TeO2 content. The lowest tendency towards crystallization was observed for the glasses containing 50 and 60 mol% TeO2. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were Zn2P2O7, BPO4 and α-TeO2. Annealing of the powdered 50ZnO–10B2O3–40P2O5 glass leads at first to the formation of an unknown crystalline phase, which is gradually transformed to Zn2P2O7 and BPO4 during subsequent heating.

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