Thermal expansion of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and the solid solution series BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7} (0{<=}x{<=}2) studied by high-temperature X-ray diffraction and dilatometry
- Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)
The thermal expansion behavior of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and BaZn{sub 2}Si{sub 2}O{sub 7} is characterized by both high-temperature X-ray diffraction (HT-XRD) and dilatometry. Ba{sub 2}ZnSi{sub 2}O{sub 7} and BaZnSiO{sub 4} show a thermal expansion (100-800 Degree-Sign C) in the range from 8.9 to 10.4 Multiplication-Sign 10{sup -6} K{sup -1}. By contrast, BaZn{sub 2}Si{sub 2}O{sub 7} has a much higher thermal expansion in the low-temperature modification and shows a phase transition at 280 Degree-Sign C which runs parallel with a steep increase in cell volume. This phase transition is also observed in the solid solution series BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7}, but it is shifted to higher temperatures and to a smaller volume change with increasing Mg{sup 2+} concentration. This solid solution series is characterized by dilatometry, X-ray diffraction and differential scanning calorimetry. An adjustment of the MgO/ZnO-ratio enables the preparation of materials with a large variety of thermal expansions. - Graphical abstract: XRD-patterns of Ba{sub 2}ZnSi{sub 2}O{sub 7} were recorded at different temperatures (left). For each XRD-pattern a Rietveld-refinement was performed, the image in the middle shows the XRD-pattern measured at room temperature (circles), the Rietveld calculation (red line) and the difference between them (blue line). The lattice parameters derived hereof were plottet against the temperature and fitted to a polynomial (right picture). From those polynomials the lattice expansion was calculated. Highlights: Black-Right-Pointing-Pointer We examined the thermal expansion of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7}. Black-Right-Pointing-Pointer Thermal expansions were determined by dilatometry and high-temperature X-ray diffraction. Black-Right-Pointing-Pointer High-temperature X-ray diffraction enabled to determine anisotropic thermal expansion. Black-Right-Pointing-Pointer BaZn{sub 2}Si{sub 2}O{sub 7} exhibits the highest thermal expansion due to a phase transition. Black-Right-Pointing-Pointer Substitution of small amounts of Zn{sup 2+} for Mg{sup 2+} leads to a decrease in thermal expansion.
- OSTI ID:
- 22012093
- Journal Information:
- Journal of Solid State Chemistry, Vol. . 188; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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