Electrical reliability and segregated manganese behavior on multilayered (Li,Na,K)NbO3 piezoceramics with Pd electrodes

Abstract

Multilayered (Li,Na,K)NbO3 lead-free piezoceramics with Pd inner-electrodes were fabricated by controlling the additive amounts of x mol% MnCO3 (x = 0.0, 0.5, 1.0, and 2.0) together with other additives. The multilayered samples containing the Mn compound had a markedly increase in electric resistivity from the order of 107 to 1011 Ω·cm at 100°C. Moreover, the normalized electric-field-induced strains for x = 1.0 were over 350 pm/V at 5 kV/mm. The Mn distributions in several multilayered samples were investigated using a scanning electron microscope with an energy dispersive X-ray spectrometry. The segregated Mn phases were observed almost in the vicinity of Pd inner electrodes. In addition, mapping of Mn content for x = 2.0 indicated that segregated Mn phases existed in the ceramic layers. We hypothesize that this complex Mn distribution was related to the results of a continuous driving fatigue test. The multilayered sample with x = 2.0 only maintained a stable state of driving current for fatigue tests over 106 cycles using 0~6 kV/mm triangle wave form at 100°C. This significant electrical reliability was provided by the segregated Mn phases in the ceramic layers.