Jia-Jun Zhou

Fabrication of nano Y–TZP materials by superhigh pressure compaction

Abstract Y–TZP nanoceramics have been fabricated by superhigh pressure compacting and pressureless sintering. It was found that, by applying superhigh pressure of about 3GPa, the green compacts with a relative density of about 60% could be obtained, which was 12% higher than that by a normal cold isostatic pressure of 450 MPa. The obvious advantage of the higher relative density of the green compact is that the sintering temperature could be decreased to as low as 1050°C. The reason for the good sintering behavior is believed to be both the increase in contact points between the particles and the decrease in pore size. Nano Y–TZP ceramics with grain size of about 80 nm could be obtained when sintered at 1050°C for 5 h.

Refreshing Piezoelectrics: Distinctive Role of Manganese in Lead-Free Perovskites

Driven by an ever-growing demand for environmentally compatible materials, the past two decades have witnessed the booming development in the field of piezoelectrics. To maximally explore the potential of lead-free piezoelectrics, chemical doping could be an effective approach, referenced from tactics adopted in lead-based piezoelectrics. Herein, we reveal the distinct role of manganese in a promising lead-free perovskite (K, Na)NbO3 (denoted by KNN) in comparison to that in market-dominating lead-based counterparts [Pb(Zr, Ti)O3, PZT]. In contrast to the scenario in PZT, manganese doping in KNN results in tremendously improved piezoelectric coefficient d33 by nearly 200%, whereas the same doping species in PZT deteriorates the d33 down to less than 30% of its original value. The result is rationalized from macroscopic and local electrical characterizations down to atomic-scale visualization. This study demonstrates that there is enormous space to further enhance piezoelectricity in lead-free systems because the chemical doping effect may completely differ in lead-containing and lead-free perovskites.