Processing and Properties of Rare Earth Ion-Doped Bismuth Titanate Thin Films by Chemical Solution Deposition method

Abstract

Ferroelectric (Bi,R) 4 Ti 3 O 12 [R: rare earth] thin films were synthesized by the chemical solution deposition (CSD) method. Heat treatment above 600 C was required for the fabrication of crystalline (Bi,R) 4 Ti 3 O 12 thin films of Bi-layered perovskite structure on Pt/TiO x /SiO 2 /Si substrates. The orientation of the films prepared at 750 C depended upon the kind of substituent rare earth ions. Bi 4:12 Ti 3 O 12 (BIT) and Bi 3:35 La 0:75 Ti 3 O 12 (BLT) thin films revealed (00l) preferred orientation. On the other hand, Bi 3:35 Nd 0:75 Ti 3 O 12 (BNT), Bi 3:35 Sm 0:75 Ti 3 O 12 (BST) and Bi 3:35 Gd 0:75 Ti 3 O 12 (BGT) thin films showed random orientation with strong (117) reflection. Synthesized (Bi,R) 4 Ti 3 O 12 films exhibited the typical ferroelectric behavior. The BNT thin film showed P r of 21.6 mC/cm 2 , which was higher than the values of the other rare earth-doped BIT thin films.

Preparation and Properties of Bi4 ? xNdxTi3O12 Thin Films by Chemical Solution Deposition

“…The well-saturated P-E hysteresis loops with a large P r and a low E c were observed for the BNT [x = 0.75, 1.0] films. Among these films, BNT [x = 0.75] thin films showed the highest remanent polarization (P r ) of 22 µC/cm 2 and a relatively low coercive electric field (E c ) of 69 kV/cm at an applied voltage of 5 V. This large ferroelectricity of current BNT films may be attributable to the change in crystal orientation from the random orientation having 00l diffractions with high intensities to the random orientation with a strong 117 reflection, and to the tilting of TiO 8− 6 octahedra derived from the substitution of Nd 3+ which has a smaller ionic radius than those of Bi 3+ [7][8][9][10]. Uchida et al achieved the P r of 24 µC/cm 2 (E c > 100 kV/cm) for 750 • C annealed BNT films prepared by the CSD [6].…”

“…Recently, the improvement of electrical properties of BIT thin films by rare-earth ion doping has been reported by several researchers [1][2][3][4][5][6][7][8][9][10]. Among them, Bi 4−x Nd x Ti 3 O 12 (BNT) has been receiving much attention due to its larger ferroelectricity than that of the other rare-earth ion doped BIT [5][6][7][8][9][10]. Therefore, the optimization of the amount of neodymium (Nd) substitution into BIT films is strongly required for the fabrication of BNT films with excellent ferroelectricity.…”

DC conduction behavior of Bi3.15Nd0.85Ti3O12 thin films grown by RF-magnetron sputtering

“…When the rare earth ions with the smaller ion radius such as Nd, Sm and Gd are substituted into the BIT, the orientation of these films was changed because of the increased lattice mismatch between the (111) plane of Pt on Ti/SiO 2 /Si substrate and (00l) plane of BIT with the substitution of rare-earth ion with the smaller ionic radius. The ionic radii of Bi 3+ and Nd 3+ are 0.135 nm and 0.127 nm, respectively [10]. Thus, the BNT thin film showed random orientation with the enhanced (117) reflection.…”

Fuel-free low-temperature self-combustion synthesis and characterization of praseodymium-substituted bismuth titanate ceramics

“…Furthermore, Yamada et al 7) and Cheng et al 8) demonstrated that remanent polarization of ceramics could be improved by substitution of rare-earth cation, such as Nd 3+ , Gd 3+ and Sm 3+ . However, to the best of our knowledge, there are limited reports on the control of anisotropic grain growth by Pr 3+ substitution in BIT.…”