Chin. Phys. B Vol. 26, No. 3 (2017) 037702 CuO added Pb 0.92 Sr 0.06 Ba 0.02 (Mg 1/3 Nb 2/3 ) 0.25 (Ti 0.53 Zr 0.47 ) 0.75 O 3 ceramics sintered with Ag electrodes at 900 ∘ C for multilayer piezoelectric actuator * Muhammad Adnan Qaiser 1 , Ahmad Hussain 1 , Yuqing Xu(徐玉青) 1 , Yaojin Wang(汪尧进) 1 , Yiping Wang(王一平) 2 , Ying Yang(杨颖) 2 , and Guoliang Yuan(袁国亮) 1, † 1 School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China 2 Precision Driving Laboratory, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China (Received 10 November 2016; revised manuscript received 21 December 2016; published online 18 January 2017) CuO added Pb 0.92 Sr 0.06 Ba 0.02 (Mg 1/3 Nb 2/3 ) 0.25 (Ti 0.53 Zr 0.47 ) 0.75 O 3 ceramics were studied to prepare high-quality multilayer piezoelectric actuators with pure Ag electrodes at 900 ∘ C. CuO addition not only reduced the sintering tem- perature significantly from 1260 ∘ C to 900 ∘ C but also improved the ceramic density to 7.742 g/cm 3 . The 0.7 wt.% CuO added ceramic sintered at 900 ∘ C shows the remnant polarization (P r ) of 40 μC/cm 2 , 0.28% strain at 40 kV/cm, and the piezoelectric coefficient (d 33 ) of 630 pC/N. This ceramic shows a strong relaxor characteristic with a Curie temperature of 200 ∘ C. Furthermore, the 0.7 wt.% CuO added ceramic and pure Ag electrodes were co-fired at 900 ∘ C to prepare a high-quality multilayer piezoelectric actuator with a d 33 of over 450 pC/N per ceramic layer. Keywords: piezoelectric ceramics, low-temperature co-fired ceramic, multilayer piezoelectric actuators PACS: 77.84.Cg, 77.80.–e, 77.65.–j, 77.22.–d DOI: 10.1088/1674-1056/26/3/037702 1. Introduction Piezoelectric actuators convert electrical energy directly into linear motion with high speed, force, and virtually unlim- ited resolution. These actuators are used in every modern high technology field from semiconductor test and inspection to super-resolution microscopy, bio-nanotechnology, and astron- omy/aerospace technology. [1,2] The actuators require high- quality piezoelectric ceramics which possess a high piezoelec- tric constant (d 33 ) and a large strain under an external electric field. [3] Extensive theoretical and practical interest has been taken in Pb-based complex perovskite solid solutions con- sisting of ferroelectric and relaxor materials, due to their ex- cellent electrical and piezoelectric properties. [4] Researchers have tried immensely hard to discover Pb-free materials with good piezoelectric property comparable to that of Pb-based ones but have failed. [5–7] Among these Pb-based materials, the (1 − x)PbMg 1/3 Nb 2/3 O 3 –xPbZr 0.52 Ti 0.48 O 3 (PMN-PZT) system has been extensively studied for actuators because of its high piezoelectricity and large strain. 0.25PMN-0.75PZT exhibits a morphotropic phase boundary (MPB) with better di- electric and piezoelectric properties than the single-phase. [8,9] The MPB of Pb(Zr 0.53 Ti 0.47 )O 3 and ferroelectric relaxation characteristics of Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) are the reasons for their excellent properties, such as a large dielectric con- stant and a broad diffuse transition. [10] Wang et al. [8] reported that Pb 0.92 Sr 0.06 Ba 0.02 (Mg 1/3 Nb 2/3 ) 0.25 (Ti 0.53 Zr 0.47 ) 0.75 O 3 ceramic sintered at 1260 ∘ C shows excellent piezoelectric and dielectric properties. Such phase boundary-induced en- hancements in a material’s properties have also been observed in other systems such as BiFeO 3 . [11,12] Generally, multilayer piezoelectric actuators require co- firing with an internal electrode such as Ag–Pd. However, the sintering temperature of PZT-based ceramic materials is at about 1200 ∘ C. [7] Mostly Ag–Pd alloy is used in multilayered actuators as the inner electrodes, but Pd is expensive, which increases the fabrication cost. [13,14] Another disadvantage of the high sintering temperature is the volatility of PbO dur- ing sintering, which pollutes the environment. In addition, the decrease of the sintering temperature can reduce energy con- sumption and environmental pollution. The multilayer piezo- electric actuator with pure Ag electrodes should be prepared at ∼900 ∘ C, since Ag evaporates rapidly above 930 ∘ C. There- fore, low-temperature processing is one of the most important techniques for the fabrication of multilayer piezoelectric actu- ators. A lot of attempts have been made to attain low tempera- ture sintering including the fine powder approach, hot press- ing and similar approaches. One such technique is the addi- tion of materials with low melting point, such as metal ox- ides, for liquid-phase sintering. [15–17] Some of the oxides and compounds are employed in assisting the liquid-phase sin- tering to reduce the sintering temperature of PZT-based ma- terials. Hayashi et al. [18] reported the addition of LiBiO 2 in Pb 0.95 Ba 0.05 (Mg 1/3 Nb 2/3 ) 0.125 Zr 0.445 Ti 0.43 O 3 ceramics sin- * Project supported by the National Natural Science Foundation of China (Grant Nos. 51472118, 51602156, 52177072, and 11274174) and the Fundamental Research Funds for the Central Universities, China (Grant Nos. 30916011104 and 30916011208). † Corresponding author. E-mail: yuanguoliang@njust.edu.cn © 2017 Chinese Physical Society and IOP Publishing Ltd http://iopscience.iop.org/cpb http://cpb.iphy.ac.cn 037702-1