Abstract: In the current study, we report on the dielectric behavior of colossal-dielectric-constant
Na1/2La1/2Cu3Ti4O12 (NLCTO) ceramics prepared by mechanochemical synthesis and spark plasma
sintering (SPS) at 850 C, 900 C, and 925 C for 10 min. X-ray powder diffraction analysis showed that
all the ceramics have a cubic phase. Scanning electron microscope observations revealed an increase
in the average grain size from 175 to 300 nm with an increase in the sintering temperature. SPS
NLCTO ceramics showed a room-temperature colossal dielectric constant (>103) and a comparatively
high dielectric loss (>0.1) over most of the studied frequency range (1 Hz—40 MHz). Two relaxation
peaks were observed in the spectra of the electrical modulus and attributed to the response of grain
and grain boundary. According to the Nyquist plots of complex impedance, the SPS NLCTO ceramics
have semiconductor grains surrounded by electrically resistive grain boundaries. The colossal
dielectric constant of SPS NLCTO ceramics was attributed to the internal barrier layer capacitance
(IBLC) effect. The high dielectric loss is thought to be due to the low resistivity of the grain boundary
of SPS NLCTO.