Low-temperature synthesis of K0.5Na0.5NbO3 ceramics in a wide temperature window via cold-sintering assisted sintering method and enhanced electrical properties

K0.5Na0.5NbO3 ceramics fabricated by combining cold sintering with annealing in air atmosphere or low pO2 atmosphere

“…Via the pressure‐assisted flowing of the liquid, the K 0.5 Na 0.5 NbO 3 particles rearrange. The dissolution–precipitation process plays a key role in CSP 20 . K 0.5 Na 0.5 NbO 3 undergoes incongruent dissolution in the liquid, and partial dissolution of K + and Na + at the interfaces of grain–liquid happens 20,21 .…”

“…The dissolution-precipitation process plays a key role in CSP. 20 K 0.5 Na 0.5 NbO 3 undergoes incongruent dissolution in the liquid, and partial dissolution of K + and Na + at the interfaces of grain-liquid happens. 20,21 As the cold-sintering temperature is increased to 180 • C, evaporation of the liquid leads to a supersaturated state, inducing precipitation of the solute onto the interfaces of the particles.…”

“…20 K 0.5 Na 0.5 NbO 3 undergoes incongruent dissolution in the liquid, and partial dissolution of K + and Na + at the interfaces of grain-liquid happens. 20,21 As the cold-sintering temperature is increased to 180 • C, evaporation of the liquid leads to a supersaturated state, inducing precipitation of the solute onto the interfaces of the particles. The stress gradient provides chemical potential that the atoms at contact points dissolve into the liquid F I G U R E 5 d 33 values of the post-annealed ceramics at room temperature (a).…”

“…employed CSP to fabricate Mn‐doped K 0.5 Na 0.5 NbO 3 ceramics through mixing the KMnO 4 solution with K 0.5 Na 0.5 NbO 3 powders, which were cold‐sintered at 120°C under 380 MPa followed by sintering at 1105°C for 4 h 19 . In our previous work, K 0.5 Na 0.5 NbO 3 ceramics were successfully prepared at the low temperatures and in a wide temperature window via cold sintering assisted sintering method with NaOH–KOH solution as liquid medium 20 . The studies demonstrate that microstructure and electrical properties of the obtained K 0.5 Na 0.5 NbO 3 ‐based ceramics are closely related to the type of transient liquids and synthesis parameters.…”

“…The system K 0.5 Na 0.5 NbO 3 always undergo incongruent dissolution in aqueous medium, and “A site” cations (i.e., K + /Na + ) tend to release in the acidic medium, whereas the dissolution rate of “B site” cation (i.e., Nb 5+ ) increases over the alkaline region 21 . As mentioned above, various transient liquids, including deionized water, 14 NaOH–KOH solution, 18,20 and KMnO 4 solution, 19 were tried during cold sintering K 0.5 Na 0.5 NbO 3 . As far as acidic liquid, acetic acid solution is one of the most commonly used solutions during CSP 22,23 .…”