High-density (1-x)(Na0.5K0.5)NbO3- xLiTaO3 [(1-x)NKN-xLT] ceramics with x = 0 - 0.2 were successfully fabricated by spark-plasma sintering (SPS). The effect of SPS on the microstructure and the piezoelectric properties of the fabricated NKN-LT ceramics are discussed and compared with those of the same NKN-LT ceramics prepared by conventional mixed-oxide ceramic processing. The morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases for the NKN-LT series was found to be in the vicinity of x = 0.06 - 0.08. The MPB was shifted to the slightly LT-rich side of that previously reported by excess addition of 2.5 mol% K2CO3. The dielectric, ferroelectric and piezoelectric properties of the NKN-LT ceramics fabricated by using the SPS process were excellent compared to those for the conventionally prepared sample. The values of ε33T/ε0, kp and Pr were 1.9, 1.4 and 2.3 times larger than the values for the conventionally prepared sample, respectively. These improvements in the ferroelectric and piezoelectric properties of the present ceramics are shown to originate from both the slight excess addition of K2CO3 and the particle orientation imparted by SPS.
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