钙掺杂对铬酸镧热膨胀系数的影响

利用固相法合成的铬酸镧粉制备铬酸镧样品。研究了钙掺杂量对铬酸镧样品热膨胀系数的影响。结果表明：当钙掺杂铬酸镧时，Ca^2＋于A位取代La^3＋，引起A位离子半径减小，晶胞参数发生变化，同时Cr^3＋变价形成Cr^4＋，引起了O^2--O^2-和Cr^3＋-O^2-键长、键角和键能相应改变，从而对铬酸镧样品的热膨胀系数和相变温度造成影响；从室温到1000℃，铬酸镧的热膨胀系数随钙掺杂量增加而增大，由正交结构向菱形结构转变的相变温度随钙掺杂量增加呈线性提高。

Effect of Ca-Doping on Coefficient of Thermal Expansion of Lanthanum Chromites

The lanthanum chromites samples were prepared by the powders synthesized by a solid-state reaction.The effect of Ca-doping on coefficient of thermal expansion(CTE) of lanthanum chromites was studied.The results showed that with the Ca-doping,A site atom La3+ in the LaCrO3 would be replaced by the Ca2+,the radius of A site was reduced and crystal parameter was changed.At the same time,the bond length,bond angel and bond energy of O2–—O2–,Cr3–—O2– were changed due to the changing of Cr3+ to Cr4+.Between room temperature to 1 000 ℃,the CTE of lanthanum chromites increased with the increase of Ca-doping content,also the phase transformation temperature of lanthanum chromites from the orthogonal structure to rhombic structure linearly increased with Ca-doping content.