Microstructure evolution and dielectric properties of K3Li2Nb5O15 and PbTiO3 composites

Investigations of composite materials with two different crystal structured ferroelectric ceramics were carried out. In this study, phase development, sintering behavior and dielectric characteristics of the composites of tungsten bronze structured ferroelectric K3Li2Nb5O15 (KLN) and perovskite structured PbTiO3 (PT) were examined as a function of molar ratio x in (1 − x) K3Li2Nb5O15–xPbTiO3. A wide range of solid solution of PT in KLN was observed and the lattice constants of KLN decreased with PT contents. However, the solubility of KLN in PT was very narrow. X-ray analysis revealed that both KLN and PT phases coexisted in the samples from x = 0.4 to x = 0.9. Therefore, two dielectric relaxation peaks were observed in the samples with x = 0.4–0.8, each of which is originated from KLN and PT phase, respectively. The addition of PT to KLN increased the maximum dielectric constant at TC and shifted the TC to lower temperature. While TC of PT rich samples were not changed significantly with KLN.