本實驗以DTA/TG 及XRD 研究Na+離子對γ→α-Fe2O3 相轉換之影響。實驗結果發現Na+會跟Fe3+離子產生取代反應，因而產生相轉換過程之中間相。含Na+離子之固態溶體，由於Na+離子之半徑較大，會阻礙γ→α-Fe2O3 相轉換時氧離子層之滑移，而無法直接完成相轉換，並提高相轉換溫度約至675℃，相轉換過程中，結晶相從尖晶石結構之立方晶相逐漸轉變成正方晶相然後再變成斜方晶相，最後轉換成剛玉結構之六方晶相的α-Fe2O3，同時析出α-NaFeO2 與Na5FeO4 之結晶相。

A precursor of the substitution of the Fe3+ ions by the Na+ ions in the Maghemite (γ-Fe2O3) was prepared using the tartrate technique. This article is focused on the transformation of γ to α-Fe2O3 phase in the progress of thermal treatment. The samples were studied using DTA/TG and X-ray diffraction (XRD). Results show that Sodium-Substituted Maghemite (Na-γ-Fe2O3) are thermally more stable than the Na-free ones and the temperature of the γ-Fe2O3 → α-Fe2O3 phase transformation increases from ~ 350℃ for pure γ-Fe2O3 to 675℃ for Na-γ-Fe2O3. However, XRD revealed the α-NaFeO2 and Na5FeO4 phases were precipitated during thermal treatment.