Effect of B 2 O 3 on phase structure and electrical properties of CuO-modified (Ba,Ca)(Ti,Sn)O 3 lead-free piezoceramics sintered at a low-temperature

High‐temperature multilayer actuators based on CuO added BiScO3–PbTiO3 piezoceramics and Ag electrodes

“…Furthermore, a series of 0.1‐0.5wt% CuO‐added BS‐PT ceramics were prepared at 930, 950, 975, and 1000°C, and only ABO 3 ‐type perovskite phase is identified in all these ceramics. These experimental results suggest that Cu 2+ ions enter the crystal lattice of perovskite structure and then change the lattice parameters of BiScO 3 –PbTiO 3 phase indeed . Cu 2+ ions would substitute Ti 4+ or Sc 3+ ions in these BiScO 3 –PbTiO 3 –based ceramics.…”

“…Furthermore, the BS‐PT:0.3wt%CuO ceramic sintered at 930°C has the density of 7.58 g/cm 3 (Figure ) which is highest among all BS‐PT: x CuO ceramics discussed above. During the BS‐PT: x CuO ceramic sintering process, the excessive CuO reacts with PbO and forms the liquid‐phase of Cu 2 O–PbO at over 680°C . The BS‐PT particles fast react with this Cu 2 O–PbO liquid to form BiSc 1− x Cu x O 3−δ –PbTi 1− y Cu y O 3−δ phase with pure ABO 3 ‐type perovskite structure, which allows the crystal grains grow and the ceramic shrinks fast.…”

“…The BS‐PT particles fast react with this Cu 2 O–PbO liquid to form BiSc 1− x Cu x O 3−δ –PbTi 1− y Cu y O 3−δ phase with pure ABO 3 ‐type perovskite structure, which allows the crystal grains grow and the ceramic shrinks fast. However, CuO, PbO, and Cu 2 O–PbO are easy to evaporate at a high temperature, and the volatile gas can result in air bubbles and cracks which decreases the ceramic density . For BS‐PT:0.3wt%CuO, the sintering temperature of 930°C is favorable to accelerate the chemical reaction and restrain the volatilization of CuO, PbO and Cu 2 O–PbO, which are two essential factors to achieve high density and high‐quality piezoelectric ceramics.…”

“…The 0.367BiScO 3 –0.633PbTiO 3 : x CuO with x = 0.1‐0.5wt% (BS‐PT: x CuO) piezoelectric ceramics were prepared by solid‐state reaction, and then the actuators with ceramic slices and Ag electrodes were prepared at 930°C . For BS‐PT: x CuO ceramics, high purity Bi 2 O 3 (99.9%, Aladin, Shanghai), Sc 2 O 3 (99.9%, Aladin, Shanghai), PbO (99.99%, Alfa Aesar, Shanghai), and TiO 2 (99.9%, Aladin, Shanghai) powders were weighed according to the BS‐PT chemical formula and milled for 12 hours.…”

“…Third, the melting point of Ag (~2 USD per gram) is 961°C and most silver glues cannot be sintered over 930°C. Therefore, it is necessary to develop a new way to decrease the sintering temperature of BS‐PT and meanwhile keep its excellent piezoelectric properties so that the cost‐effective actuator with BS‐PT slices and Ag electrodes can be sintered at ≤930°C . Recently CuO, LiBiO 2 , Li 2 CO 3 , Bi 2 O 3 , and MnO 2 oxides were often added to raw oxide materials to reduce the ceramic sintering temperature recently, and thus BS‐PT and these oxides may be co‐fired at ≤930°C to achieve the high‐quality piezoelectric ceramics and their actuators.…”