Effect of Sc Doping on the Structure and Electrical Properties of (Na0.85K0.15)0.5Bi0.5TiO3 Thin Films Prepared by Sol–Gel Processing

Authors

  • Yunyi Wu,

    Corresponding author
    1. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
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  • Xiaohui Wang,

    1. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
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  • Longtu Li

    1. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
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  • N. Alford—contributing editor

  • This work was supported by the National Science Fund for Distinguished Young Scholars (Grant No. 50625204), Science Fund for Creative Research Groups (Grant No. 50921061), the Ministry of Science and Technology of China through 973-project under Grant 2009CB623301, Outstanding Tutors for doctoral dissertations of S&T project in Beijing (No. YB2081000302), Tsinghua university initiative scientific research program (No. 303002261), and China Postdoctoral Science Foundation (No. 20100470349).

†Author to whom correspondence should be addressed. e-mail: wuyunyi_80@yahoo.com.cn

Abstract

(Na0.85K0.15)0.5Bi0.5TiO3 (NKBT) and B-site-substituted NKBT by Sc, i.e. (Na0.85K0.15)0.5Bi0.5Ti(1−x)ScxO3 (NKBT-Scx, x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.4) thin films were prepared on Pt/Ti/SiO2/Si(100) substrates by an aqueous sol–gel method. Structures and electrical characteristics of the films were studied as functions of Sc composition. Structures were investigated by X-ray diffraction (XRD), scanning probe microscopy, scanning electron microscopy, and Raman spectroscopy. XRD indicates that a secondary phase peak appears when Sc-doping concentration increases above x=0.25 due to the limited substitution tolerance of Sc3+ for Ti4+. With increasing Sc-doping composition, generally, the octahedra-related vibration modes show a high-frequency shift. The remnant polarization (Pr) value is a maximum for the NKBT-Sc0.25 films of 18.62 μC/cm2 and decreases with both decreasing and increasing doping concentration. The NKBT-Sc thin film with an optimized Sc-doping concentration of x=0.25 shows the effective piezoelectric coefficient d33* of 67 pm/V. The Curie temperature (Tc) of the NKBT thin film shifted to higher temperature by adding Sc dopant.

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