Phase transition behavior of (K,Na)NbO^sub 3^-based high-performance lead-free piezoelectric ceramic composite with different phase compositions depending on Na fraction

• Published in: Japanese Journal of Applied Physics Vol. 57; no. 1; p. 011502
• Main Authors: Yamada, Hideto, Matsuoka, Takayuki, Yamazaki, Masato, Ohbayashi, Kazushige, Ida, Takashi
• Format: Journal Article
• Language: English
• Published: Tokyo Japanese Journal of Applied Physics 01.01.2018
• Subjects: Barium zirconates; Computer simulation; Domain walls; Hematite; Image resolution; Iron oxides; Lead free; Microstructure; Niobium oxides; Perovskites; Phase transitions; Piezoelectricity; Superlattices; Transmission electron microscopy
• ISSN: 0021-4922

The structures of the main (K1− x Nax)NbO3 perovskite in a high-performance lead-free piezoelectric ceramic composite (K1− x Nax)0.86Ca0.04Li0.02Nb0.85O3−δ-K0.85Ti0.85Nb1.15O5–BaZrO3–MgO–Fe2O3 (x = 0.52 and 0.70) with trace amounts of LiMgFeTiO4 inverse spinel and (Li,K)2(Mg,Fe,Ti,Nb)6O13 layered structure have been investigated by transmission electron microscopy (TEM) and synchrotron powder X-ray diffractometry (XRD) with varying temperatures. The bright-field TEM images have shown tetragonal 90°-domain contrasts at 80 and 40 °C, and the XRD profile has been simulated by adding an average structure of two differently oriented tetragonal structures bound by a 90°-domain wall for the x = 0.52 sample. Aggregates of tilted NbO6 nanodomains have been observed in a high-resolution TEM image, and the crossover of P4mm–Amm2 features from 60 to 20 °C and diffuse 2 × 2 × 2 superlattice reflections of the tilted NbO6 Imm2 structure have been observed in XRD data for the x = 0.70 sample.