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Effect of Mn Doping on Microstructure and Electrical Properties of the (Na 0.85 K 0.15 ) 0.5 Bi 0.5 TiO 3 Thin Films Prepared by Sol–Gel Method
Author(s) -
Wu Yunyi,
Wang Xiaohui,
Zhong Caifu,
Li Longtu
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.04576.x
Subject(s) - materials science , raman spectroscopy , dielectric , ferroelectricity , analytical chemistry (journal) , doping , microstructure , thin film , perovskite (structure) , impurity , dielectric loss , coercivity , mineralogy , crystallography , nanotechnology , chemistry , optics , condensed matter physics , metallurgy , physics , optoelectronics , organic chemistry , chromatography
x mol% Mn‐doped (Na 0.85 K 0.15 ) 0.5 Bi 0.5 TiO 3 (NKBT–Mn x , x =0, 2, 4, 6, 8, and 10) thin films were deposited on Pt(111)/Ti/SiO 2 /Si substrates via an aqueous sol–gel method. The effects of Mn contents on the microstructure and electrical properties of NKBT films are investigated in detail. X‐ray diffraction indicates that B‐site Mn substitutions do not change the perovskite structure. However, when Mn‐doping concentration above 6 mol%, the impurity phase of Mn oxide exist. Raman spectra show that a new Raman mode at about 706 cm −1 appears with Mn doping. And the gradual enhancement of this new Raman mode with increasing Mn‐doping concentration confirmed the Mn substitution for B‐site Ti in NKBT thin films. The ferroelectric measurement of the films indicated that, with the increase of Mn‐doping concentration, the remnant polarization P r values increased firstly with a maximum value at 6 mol% and then decreased. The optimal ferroelectric properties was obtained in the film with x =6, giving the remnant polarization ( P r ) and coercive field ( E c ) values of the films of 19.2 μC/cm 2 and 106 KV/cm, respectively. According to dielectric measure, it is noted that the NKBT film with 6 mol% Mn doping exhibits the best dielectric property with dielectric constant of 492 and dielectric loss of 0.051. Owing to the reduction of transition from Ti 4+ to Ti 3+ and reducing the number of intrinsic oxygen vacancies, the NKBT–Mn6 shows lower leakage current density than NKBT thin film. A typical “butterfly” shape displacement–voltage loop was observed for the film samples, and piezoelectric response shows similar trend to the dielectric response with the increase of Mn‐doping concentration.