Negative Thermal Expansion of (ZrMg) _xY_2–2xMo₃O₁₂ Ceramics with Low Hygroscopicity

Abstract

(ZrMg) _xY_2–2xMo₃O₁₂ (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1) ceramics have been synthesized to obtain less hygroscopicity and negative thermal expansion. With increasing the substitution of (ZrMg)⁶⁺ (ion radius 7.2 ×10^–11 m) for Y³⁺ (ion radius 9×10⁻¹¹ m), the crystal water are reduced obviously. The linear thermal expansion coeffcient is improved with increasing the content of (ZrMg)⁶⁺. The material shows near zero thermal expansion (−0.12×10⁻⁶ K⁻¹, 430–870 K) with x=0.7. Meanwhile, ZrMgMo₃O₁₂ shows low non-hygroscopicity and negative thermal expansion, but low softening temperature. After substituting amount of Y³⁺ for (ZrMg)⁶⁺ in ZrMgMo₃O₁₂ (x=0.8), the softening temperature increases remarkably (750 K to 830 K) and it presents near zero thermal expansion.

Keywords

negative thermal expansion / hygroscopicity / raman spectroscopy / ceramics