Effect of CuO on the Sintering Temperature and Piezoelectric Properties of (Na_0.5K_0.5)NbO₃ Lead‐Free Piezoelectric Ceramics

Abstract

When a small amount of CuO was added to (Na 0.5 K 0.5 )NbO 3 (NKN) ceramics sintered at 9601C for 2 h, a dense microstructure with increased grains was developed, probably due to liquidphase sintering. The Curie temperature slightly increased when CuO exceeded 1.5 mol%. The Cu 21 ion was considered to have replaced the Nb 51 ion and acted as a hardener, which increased the E c and Q m values of the NKN ceramics. High piezoelectric properties of k p 5 0.37, Q m 5 844, and e 3 T /e 0 5 229 were obtained from the specimen containing 1.5 mol% of CuO sintered at 9601C for 2 h.

The phase structure and electric properties of low-temperature sintered (K, Na)NbO3-based piezoceramics modified by CuO

“…The increased T T À O of LKNNTAS-CuO piezoceramics indicates that the orthorhombic phase is dominant at room temperature, in consistent with the analysis of XRD patterns. The dielectric properties of LKNNTAS piezoceramics decrease with the addition of CuO, showing similar tendency to the previous work [15][16][17]. P r are 12.6 μC/cm 2 and 13.0 μC/cm 2 , respectively.…”

“…On the other hand, CuO has been proved as an effective sintering aid for many kinds of piezoceramics. But it is also reported that the addition of a large amount of CuO will induce undesirable secondary phases, which deteriorates piezoelectric properties [15][16][17]. According to the above considerations, proper …”

Low Temperature Sintering of the Alkali-Niobate Ceramics

“…4.5. However, the T c did not C for 10 h [15] increase further as the CuO addition increased, indicating that only a small amount of Cu ion was incorporated into the NKNC matrix. Since the radius of the Cu 2+ ion (0.73 Å ) is similar to that of the Nb 5+ ion (0.64 Å ), the Cu 2+ ion is thought to replace the Nb 5+ ions and transform the NKNCs into hard ceramics.…”

“…4.4 [15]. However, when the CuO content exceeded 1.0 mol%, peaks for the CuO second phase indicated by the arrows, were observed.…”

Review: environmental friendly lead-free piezoelectric materials

“…CuO is often used because of its low melting point and formation of liquid phase. Park et al [75] elaborately studied the effect of CuO on KNN ceramics. They observed that addition of CuO decreases the sintering temperature of KNN below 1000°C in order to prevent the Na 2 O evaporation and to eventually improve the piezoelectric properties by increasing their polling efficiency.…”