Influence of tantalum on mechanical, ferroelectric and dielectric properties of Bi-excess Bi3.25La0.75Ti3O12 thin film

Abstract The Bi-excess Bi 3.25 La 0.75 Ti 3 O 12 (BLT) and Bi 3.25 La 0.75 Ti 2.91 Ta 0.09 O 12 (BLTT) thin films were deposited on Pt(1 1 1)/Ti/SiO 2 /Si substrates using rf-magnetron sputtering method. The effect of tantalum on mechanical, ferroelectric and dielectric properties of BLT thin films was investigated. XRD patterns reveal that BLT and BLTT thin films have a same second crystalline phase Bi 12 TiO 20 , but the former has a randomly oriented major Bi 4 Ti 3 O 12 phase while the major phase in the later is preferentially oriented along 〈1 1 7〉 direction. XPS analysis shows that the substitution of Ta 5+ has a significant influence on Ti 3+ defects. Mechanical response of thin films is discussed in the light of nano indentation analysis which shows that both the hardness and modulus are reduced with the addition of Ta 5+ . Ferroelectric properties were improved significantly by Ta 5+ doping due to the reduction of Ti 3+ defects, and an enhanced remnant polarization (2 P r ) of 32.5 μC/cm 2 and a decreased coercive field (2 E c ) of 260 kV/cm were obtained. In addition, the Ta substitution elevated the dielectric constant and slightly raised the Curie temperature.