Structural evolution and phase transition of Sr3Sn2O7 doped with Ca

Highlights: • The phase transition temperature of Sr₃Sn₂O₇ is increased by Ca doping • Ca doping deepens the rotation of oxygen octahedron along the c axis. • The space group of Sr₃ Sn₂ O₇ above 407.9 k is I4/mmm. • Phonon mode $A_1^{\left(2\right)}$ and $A_2^{\left(2\right)}$ are related to the phase transition. The ceramics of Sr_3-xCa_xSn₂O₇ (x = 0,0.1,0.2,0.3,0.6,0.8,1) were synthesized by solid-state reaction method. The lattice constants of Sr_3-xCa_xSn₂O₇ decrease, and the rotation of oxygen octahedron around c axis increases with the increasing of Ca doping. The phase transition temperature of Sr_3-xCa_xSn₂O₇ increases 183.3 K with the increase of Ca doping concentration from × = 0 to × = 0.3. The space group of Sr₃Sn₂O₇ changed from A2₁am to I4/mmm at 407.9 K. Near the phase transition temperature, the Raman shift of phonon mode $A_1^{\left(2\right)}$ of Sr_3-xCa_xSn₂O₇ changes abruptly, and the phonon mode $A_2^{\left(2\right)}$ disappears gradually.