  Temperature-dependent dielectric permittivity of lead-free (LixNa1-x)NbO3 for
nominal x = 0.04-0.20, prepared by solid state reaction followed by sintering,
was studied to resolve often debated issue pertaining to exactness of
morphotropic phase boundary (MPB) location along with structural aspects and
phase stability in the system near MPB. Interestingly, a diffuse phase
transition has been observed in the dielectric permittivity peak arising from
the disorder induced in A-site and structural frustration in the perovskite
cell due to Li substitution. A partial phase diagram has been proposed based on
temperature-dependent dielectric permittivity studies. The room temperature
piezoelectric and ferroelectric properties were investigated and the ceramics
with x = 0.12 showed relatively good electrical properties (d33 = 28 pC/N, kp =
13.8%, Qm = 440, Pr = 12.5 {micro}C/cm2, EC = 43.2 kV/cm, Tm = 340 oC). These
parameter values make this material suitable for piezoelectric resonator and
filter applications. Moreover, a high dielectric permittivity (= 2703) with
broad diffuse peak near transition temperature along with low dielectric loss
(< 4%) in a wide temperature range (50-250 oC) found in this material may also
have a potential application in high-temperature multilayer capacitors in
automotive and aerospace related industries.
