Low-temperature sintering of alkaline niobate based piezoelectric ceramics using sintering aids

Three kinds of sintering aids, LiBiO2, CuBi2O4 and LiBO2, were selected as sintering aids for the low temperature sintering of (Li0.04K0.52Na0.44)(Nb0.84Ta0.1Sb0.06)O-3 (LF4) ceramics and the effects of these compounds on the sintering behavior of the LF4 ceramics was investigated. The addition of LiBiO2 decreased the sintering temperature of LF4 about 100 degrees C but the effect was limited and the broadening of XRD peaks due to the degradation of crystallinity was observed. The CuBi2O4 was also effective to decrease the sintering temperature of LF4 ceramics but a secondary phase was formed when a large amount of CuBi2O4 was added. The addition of a small amount of LiBO2 was very effective to decrease the sintering temperature of LF4 ceramics. By optimizing the sintering conditions, ceramics with the relative density of 95% were obtained at 950 degrees C which was lower than the melting point of Ag. Li ions in LiBO2 were incorporated into the LF4 lattices, giving rise to the degradation of piezoelectric properties through the change of crystalline phase. The addition of excess Na with LiBO2 restricted the incorporation of Li ions into the lattice. Ceramics sintered at 950 degrees C showed the relative permittivity of 738 and the d(33) constant of 138 pC/N at room temperature. (C) 2008 The Ceramic Society of Japan. All rights reserved.