Temperature‐dependent Raman scattering in ferroelectric Bi4−xNdxTi₃O₁₂(x = 0, 0.5, 0.85) single crystals

The temperature‐dependent Raman spectra of ferroelectric Bi 4− x Nd x Ti 3 O 12 ( x = 0, 0.5, 0.85) single crystals were recorded from 100 to 800 K. It was found that there is a critical Nd content x 0 between 0.5 and 0.85. The Nd 3+ ions prefer to replace Bi 3+ ions in pseudo‐perovskite layers when x < x 0 , while they might begin to incorporate into (Bi 2 O 2 ) 2+ layers when x ≥ x 0 . Nd substitution leads to a decrease in the ferroelectric–paraelectric transition temperature ( T c ). A monoclinic distortion of orthorhombic structure occurs in Bi 4 Ti 3 O 12 crystals at temperatures below 200 K.