High piezoelectricity of low-temperature sintered Li2CO3-added PNN–PZT relaxor ferroelectrics

High piezoelectric properties ( d 33 = 936 pC/N, d 33 * = 1015 pm/V, and k p = 0.701) are obtained from 960 °C sintered PNN–PZT piezoceramics by adding Li 2 CO 3 . The introduction of Li + ions into PNN–PZT ceramics causes the phase shifts to the morphotropic phase boundary (MPB) region, which has not been reported for lead-based ferroelectrics. The Li + ion doping shifts the phase to the MPB region, which grows the grains and decreases the activation energy ( E a ) of the domain wall motion, making the domain grow more easily. Meanwhile, the domain indicates that Li + ion doping allows the domain to rotate more easily; therefore, the domain size grows from the nanometer to the micrometer regime. Unlike reported nano-domains that lead to high piezoelectric activities, the MPB and larger micro-domains in the PNN–PZT ceramics are responsible for the high piezoelectric response.