Effects of Zr substitution on structures and ferroelectric properties of Bi3.25La0.75Ti3O12 thin films

Thin films of Bi3.25La0.75Ti3O12 (BLT) and B-site substituted BLT by Zr, i.e. Bi3.25La0.75Ti3-xZrxO12 (BLTZx, x = 0.20, 0.50, 0.75, 1.00 and 1.50) were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Structures and electrical characteristics of the polycrystalline films were studied as functions of Zr composition. Structures were investigated by x-ray diffraction, scanning electron microscopy and Raman spectroscopy. It is revealed that the Zr substitution does not destroy the layered structures of BLT but the Zr substitution tolerance is limited. With increasing Zr composition, generally, the octahedra-related vibration modes show a significant low-frequency shift. Compared with the well-known BLT films, the BLTZ0.20 films have larger remnant polarization (Pr), smaller coercive field (Ec) and better fatigue resistance. However, further increasing Zr composition leads to weakened ferroelectricity of the BLTZx films with decreased Pr and reduced fatigue resistance. The effects of Zr substitution on structures and ferroelectric properties of BLT and the correlation between structures and properties are discussed in detail