Piezo and pyroelectricity in spark plasma sintered potassium sodium niobate (KNN) ceramics

We report fabrication and piezo- and pyroelectric characterizations of spark plasma sintered (SPS) lead-free K
_0.5
Na
_0.5
NbO
₃
(KNN) ceramics. SPS sintering produced dense KNN (99% of the theoretical density) at sintering temperature as low as 900°C. A significant improvement in the dielectric, piezoelectric and pyroelectric properties is observed after annealing the sample at 925°C. The measured piezoelectric coefficient d
₃₃
and pyroelectric coefficient of poled KNN ceramic are 94 pC/N and 22.84 μCm
^-2
K
^-1
, respectively. These values are high enough to focus on the further enhancement of the material properties through adequate control of the phase structure of the material for lead-free energy harvesting applications.