Zero Thermal Expansion In Zrmg1-Xznxmo3o12

Ceramics with near-zero thermal expansion are rare, especially when this feature includes near room temperatures. Phases from A(2)M(3)O(12) and ABM(3)O(12) were identified as candidates for near-zero thermal expansion due to their structural features.It is supported by in situ X-ray Powder Diffraction and Raman Spectroscopy data that the ZrMg1-xZnxMo3O12 system (0 <= x <= 0.3) presents zero thermal expansion over a wide temperature range, including room temperature. Partial substitution of Mg2+ in octahedral sites by larger Zn2+ is followed by unexpected unit-cell contraction, possibly due to covalency contraction effect of Zn-O bonds.ZrMgMo3O12 presents alpha(l) = - 4.28 x 10(-7) degrees C-1, while partial substitution reduced alpha(l) to the values as low as - 2.02 x 10 (-7) degrees C-1 and - 2.54 x 10(-7) degrees C-1 for x = 0.1 and x = 0.2, respectively. This feature might be ascribed to covalency contraction of Zn-O bonds and increase of rigidity of octahedra. High-temperature Raman spectroscopy revealed blue-shift of some frequency modes, responsible for near-zero thermal expansion in this system.This system is a good candidate for thermal shock resistance application, since presents near-zero thermal expansion and does not show phase transition close to room temperature and is not hygroscopic.