Piezoelectric and dielectric properties of Sn-doped (Na_(0.5)K_(0.5))NbO_3 ceramics processed under low oxygen partial pressure atmosphere

摘要

Sn-doped (Na_(0.5)K_(0.5))NbO_3 (Sn-NKN) ceramics fired under various oxygen partial pressure (pO_2) conditions have been investigated and discussed in terms of bulk piezoelectric and dielectric properties. X-ray diffraction measurements and Rayleigh analysis indicate that the substitution site of the Sn cations depend on the pO_2 atmosphere in the firing process. For pO_2 higher than 1.0×10~(-10)atm, Sn cations mainly substitute as Sn~(4+) at the B-site of perovskite NKN, whereas Sn~(2+) A-site substitution is favored under a low-pO_2 atmosphere. Low-pO_2 fired Sn-NKN ceramics exhibit higher relative permittivity, Curie temperature, and piezoelectric coefficient (d_(33)). Sn~(2+) at A-site acts as a donor and reduces the p-type carrier concentrations that result from an electronic compensation of metal vacancies created through the high volatility of Na and K suboxides. The higher piezoelectricity and resistivity in low-pO_2 fired Sn-NKN ceramics make this material suitable for base-metal cofired devices such as Ni-inner-electrode multilayer capacitors and actuators.