Nd掺杂对Bi4Ti3O12铁电薄膜的微结构和铁电性能的影响

利用溶胶-凝胶法在Pt/Ti/SiO₂/Si(100)衬底上制备了Nd掺杂Bi₄Ti₃O₁₂(Bi_4-xNd_xTi₃O₁₂, x=0.00,0.30,0.45,0.75,0.85,1.00,1.50)铁电薄膜样品.研究了Nd掺杂对Bi₄Ti₃O₁₂薄膜的微结构和铁电性能的影响.研究结果表明:Nd掺杂未改变Bi₄Ti₃O₁₂薄膜的基本晶体结构.在掺杂量x<0.45时,Nd³⁺只取代类钙钛矿层中的A位Bi³⁺.当x=0.45时,样品剩余极化强度达最大值,在270kV·cm^-1的电场下为32.7μC·cm^-2.掺杂量进一步增加时,结构无序度开始明显增大,Nd³⁺开始进入(Bi₂O₂)²⁺层,削弱其绝缘层和空间电荷库的作用,导致材料剩余极化逐渐下降.当掺杂量x达到1.50时,掺杂离子最终破坏(Bi₂O₂)²⁺层的结构,材料发生铁电-顺电相变.

Effects of neodymium doping on microstructures and ferroelectric properties of bismuth titanate ferroelectric thin films

The Bi_4-xNd_xTi₃O₁₂(x=0.00,0.30,0.45,0.75,0.85,1.00,1.50) ferroelectric thin films were prepared on the Pt/Ti/SiO₂/Si(100) substrates using sol-gel method. The effect of neodynium doping on the microstructures and ferroelectric properties of films were studied. The experimental results show that Nd³⁺ only substitutes Bi³⁺ in the pseudo-perovskite block when Nd content x is lower than 0.45. When Nd content x is about 0.45, the film has the largest remnant polarization (2P_r) of 32.7μC·cm^-2 at an applied field of about 270kV·cm^-1. At x>0.45, part of Nd ions are incorporated into the (Bi₂O₂)²⁺block, which would change the microstructure of (Bi₂O₂)²⁺ block and weaken its functions as the insulating layer and the space charge storage, resulting in the decrease of the 2P_r. When x=1.50, the dopout would destroy the structure of (Bi₂O₂)²⁺ block, which leads to ferroelectric-paraelectric phase transition of the film.