Effects of Cr and Nb doping on the ferroelectricity of chemical-solution-deposited Bi 3.5Nd 0.5Ti 3O 12 films

Abstract

The effects of Cr and Nb doping and annealing processing on the microstructure and ferroelectricity of Bi 3.5Nd 0.5Ti 3O 12 (BNT) films deposited by chemical-solution method were studied. The BNT films deposited from 0.05 M solutions showed larger grain size and thus better ferroelectricity than those deposited from 0.075 M solutions. For the Cr-doped BNT (BNTC x) films only Cr 3+ substitutionally incorporated into the Ti 4+ site of the TiO 6 octahedron. Cr doping could result in the increase of the number of oxygen vacancies, reduction of the grain size, and enhancement of c-axis oriented growth, leading to the degradation of the remanent polarization (2Pr) of BNTC x films. For the Nb-doped BNT (BNTN x) films the 2Pr first increased from 40 μC/cm 2 at x = 0–43 μC/cm 2 at x = 0.005 and then decreased with increasing the Nb concentration ( x) in the range of 0.01–0.1. The Nb cations substitutionally incorporated into the Ti 4+ site of the BNT lattice were in the state of Nb 5+, which could reduce the amount of oxygen vacancies and thus improve the 2Pr. The doping of Nb 5+ into the BNT films could induce four effects on the 2Pr, i.e., reducing the amount of oxygen vacancies, reducing the grain size, enhancing the (1 0 0)/(0 1 0)-oriented growth, and possibly changing the lattice distortion of the TiO 6 octahedron.