High‐Performance Small‐Amount Fe2O3‐Doped (K,Na)NbO3‐Based Lead‐Free Piezoceramics with Irregular Phase Evolution

• DOI: 10.1111/jace.14230
• Publication Date: 2016-03-26T12:47:29Z
• Authors: Jinming Guo; Fang Xu; Xunzhong Shang; Yinmei Lu; Pai Li; Taosheng Zhou; Zaoli Zhang; Yunbin He
• Keywords: 0103 physical sciences; 02 engineering and technology; 0210 nano-technology; 01 natural sciences

[(K0.43Na0.57)0.94Li0.06][(Nb0.94Sb0.06)0.95Ta0.05]O3 + x mol% Fe2O3 (KNLNST + x Fe, x = 0~0.60) lead‐free piezoelectric ceramics were prepared by conventional solid‐state reaction processing. The effects of small‐amount Fe2O3 doping on the microstructure and electrical properties of the KNLNST ceramics were systematically investigated. With increasing Fe3+ content, the orthorhombic‐tetragonal polymorphic phase transition temperature (TO‐T) of KNLNST + x Fe ceramics presented an obvious “V” type variation trend, and TO‐T was successfully shifted to near room temperature without changing TC (TC = 315°C) via doping Fe2O3 around 0.25 mol%. Electrical properties were significantly enhanced due to the coexistence of both orthorhombic and tetragonal ferroelectric phases at room temperature. The ceramics doped with 0.20 mol% Fe2O3 possessed optimal piezoelectric and dielectric properties of d33 = 306 pC/N, kp = 47.0%, = 1483 and tan δ = 0.023. It was revealed that the strong internal stress in the KNLNST + x Fe ceramics with higher Fe3+ contents (x = 0.40, 0.60) stabilized the orthorhombic phase, leading to the irregular “V” type rather than the usually observed monotonic phase transition with composition change in the ceramics.