Fabrication of lead-free piezoelectric (Na0.5K0.5)NbO3 ceramics by a modified solid-state reaction method

Sodium potassium niobate, (Na
_0.5
K
_0.5
)NbO
₃
, fine powder has been successfully synthesized at the low temperature of 550degC through a modified solid-state reaction method, in which urea [CO(NH
₂
)
₂
] plays an important role. High-density (Na
_0.5
K
_0.5
)NbO
₃
ceramics could be obtained by conventional sintering of the synthesized (Na
_0.5
K
_0.5
)NbO
₃
fine powder with the addition of 0.03 mol% Co
₃
O
₄
as a sintering additive. The crystal structure, microstructure, and dielectric and piezoelectric properties were characterized. The (Na
_0.5
K
_0.5
)NbO
₃
ceramic showed a comparatively saturated P-E hysteresis loop. The (Na
_0.5
K
_0.5
)NbO
₃
ceramic also displayed piezoelectricity with a piezoelectric constant d
₃₃
of 126 pC/N and a planar electromechanical coupling factor k
_p
of 33%.