负热膨胀材料Sm_(0.85)Sr_(0.15)MnO_(3-δ)制备及热膨胀性能研究

A Novel Negative Thermal Expansion Material Sm_(0.85)Sr_(0.15)MnO_(3- δ): Synthesis and Thermal Property

以Sr2＋部分替代SmMn03中的Sm3＋，采用固相法成功制备出新的负膨胀材料Smo85Sro15Mn03-δ其线膨胀系数为-10．08×10-6／K（360～873K）；SEM观察其组织为单一的球状或椭球状颗粒；其相对密度为95．5％；XRD和EDS分析表明，smo85Sr0.15Mn036为正交结构（空间群pbnm）；DSC和TGA曲线支持了smo85Sr0.15MnO3—6在温度升高时Mn^4＋O6八面体畸变及氧缺陷的存在。Sm085Sr0.15，Mn03—6的热膨胀机制为晶格振动和Mn离子间电子转移两个因素共同作用：当温度低于360K时，随着温度的升高，晶格振动加剧引起晶胞体积增大占优，Sm0.85Sr0.15MnO3-δ呈现低正膨胀性能；当温度高于360K时，随着温度的升高，Mn4＋转化成Mn3＋的离子数增加，导致Mn3＋O6八面体畸变增大甚至产生氧缺陷，使得晶格体积变小占优，sm0.8Sr0.15Mn03—6呈现负膨胀性能。

A novel negative thermal expansion （NTE） materialSm0.85Sr0.15Mn03-δ was synthesized by solid-state method. It is originated in SmMnO3with Sr2 ＋ partly substituting Sm3＋. Ceramic Sm0. 85Sr0 15 MnO3-δexhibits NTE coefficient of - 10.08 × 10-6/K from 360 to 873 K, which crystallizes in orthorhombic structure （space group pbnm） with regular morphology and uniform grain size. The relative density measured by Archimedes drainage method is 95.5%. The results of X-ray diffraction and TGA/DSC tests suggest the negative thermal expansion phenomenon relates to the electron transfer of Mn4＋ ions. Mn4＋ dramatically converts into Mn3. accompanied by Mn3＋ 06octahedral distortions and oxygen defects with temperature increasing, it is found that the sample volume continually decreases.