High-Performance BCZT-based Lead-Free Piezoelectric Ceramics With Low Sintering Temperature

Researching on lead-free piezoelectric ceramics to replace traditional Pb-basedmaterials is a hot topic due to the demand of environment protection. BCZT ceramicshas been reported to possess very high piezoelectric properties and is a promisinglead-free piezoelectric system. In this work, based on BCZT system, ceramics withimproved properties were fabricated by adding CuO sintering aid, adding KNNLSTand Mn ion doping.Based on BCZT ceramics, lead-free piezoelectric ceramics were fabricated byadding CuO as sintering aid. The addition of CuO lowered the sintering temperature.The ceramics could be sintered at1350oC, and denser ceramics were obtained. Cu²⁺replaced Ti4+to produce lattice distortion, and the phase of ceramics was changedfrom rhombohedral to tetragonal. Rhombohedral and tetragonal phases coexisted inceramics with a small mount of CuO. The ceramics exhibit good electrical properties,with piezoelectric cinstant d₃₃=340pC/N, dielectric constant ε_r=3147, dielectric losstanδ=0.025, Curie temperature T_c=92oC. So adding CuO can improve the sinteringand electrical properties of BCZT ceramics.Based on BCZT system, lead-free piezoelectric ceramics were fabricated byadding KNNLST. The results showed that KNNLST-doping enhanced the graingrowth, and the ceramics became denser. KNNLST addition caused lattice distortion,and as a result, the rhombohedral-tetragonal polymorphic phase transitiontemperature T_R-Twas shifted near room temperature. The ceramics with a smallmount of KNNLST doping exhibited optimum piezoelectric properties, withpiezoelectric constant d₃₃=464pC/N and planar electromechanical coupling factork_p=0.44.Based on BCZT system, lead-free piezoelectric ceramics were fabricated by Mnion doping. A small mount of Mn ion could dissolve into BCZT lattice and a formpure perovskite structure. Mn ion doping caused lattice distortion, and as a result, therhombohedral-tetragonal polymorphic phase transition temperature T_R-Twas shiftednear room temperature. The ceramics with Mn content x=0.005possessed goodpiezoelectric properties with piezoelectric constant d₃₃=380pC/N.In addition, Li-doping BNT-BKT-BT lead-free piezoelectric ceramics werefabricated with sol-gel method, and the properties of the gel, the precursor powderand the ceramics were studied. The precursor powder fabricated with sol-gel method was of nano scale, and this contributed to lower the sintering temperature. Theaddition of Li further improved the sintering of ceramics, and at the same timeenhanced the electrical properties. The ceramics with Li content x=0.05possessedgood electrical properties, with piezoelectric constant d₃₃=192pC/N, planarelectromechanical coupling factor k_p=0.30and dielectric constant ε_r=1239.