Strain‐Induced Relaxor Behavior in PbSc_0.50Nb_0.25Ta_0.25O₃ Thin Films: A Comparison with Nanoceramics

Abstract

Comparative studies of the microstructure, micro‐Raman spectroscopy, and dielectric properties of PbSc0.50Nb0.25Ta0.25O3 (PSNT) thin films and nanoceramics were carried out over a wide range of temperature (100–520 K) and frequency (100 Hz to 1 MHz). The microstructure of PSNT films revealed an in‐plane compressive strain, whereas PSNT nanoceramics showed an average grain size of 10–15 nm although these nanoordered regions are not capable of producing relaxor behavior. We have observed a shift of 65 K in the dielectric maxima temperature in PSNT films toward the lower temperature side compared with bulk, which confirms the in‐plane compressive strain in the films. We have proposed a dielectric model to calculate the shift in dielectric maxima temperature. Using our experimental data of PSNT thin films, the theoretical model predicted a shift of 62 K in the dielectric maxima temperature, which matched well with our experimental observation. The modified Curie–Wiess law showed a broad relaxation (γ∼2) and a higher disorder level (δ=90 K) for PSNT thin films compared with PSNT nanoceramics having γ∼1.60 and δ=15 K. Well‐behaved hysteresis loops were observed in a broad temperature range for PSNT thin films and slim hysteresis for nanoceramics, indicating a relaxor ferroelectric and diffused ferroelectric phase transition (DFPT) nature, respectively. The temperature‐dependent micro‐Raman spectroscopy revealed that the ferroelectric state in PSNT nanoceramics was accompanied by the appearance of a new peak as a shoulder at ∼80 cm−1 to the lowest F2g mode ∼57 cm−1. Its half‐widths and intensity reduced to zero near the phase transition temperature, whereas the A1g mode showed a doublet namely at (805 and 830 cm−1) below DFPT and an intermediate singlet frequency at 820 cm−1 above DFPT. The micro‐Raman spectra for the thin film matched quite well with the nanoceramics, except that the missing second F2g mode at ∼360 cm−1 was interpreted due to a shorter coherence length in the dipole arrangement in thin films. The in‐plane compressive strain, dipole arrangement, and the size of the nanoordered regions vary the dielectric response of the PSNT films compared with the nanoceramics.

A comprehensive investigation on the phase transformation behavior and electrical properties of (Pb1−xBax)ZrO3 (≤x≤0.5) thin films

“…With the increase of mismatch effect between the films and substrates, the grain size became smaller. 20,21 In the work of Ziebert et al 22 on ͑Pb, Ca͒TiO 3 ͑PCT͒ and Pb͑Sc, Nb͒O 3 ͑PSN͒ films, it was also found that the FE relaxor behavior was grain size dependent. 18,19 In order to give a better illustration of the broadening of the diffuse phase transformation, the curves of the reduced dielectric constant ͑ / max ͒ at 1000 kHz as a function of the reduced temperature ͓ = ͑T − T m ͒ / T m ͔ are given in Fig.…”

High Tunability in (111)‐Oriented Relaxor Pb0.8Ba0.2ZrO3 Thin Film with Antiferroelectric and Ferroelectric Two‐Phase Coexistence

“…Typical ferroelectric relaxor character can be observed around the dielectric permittivity peak, in contrast, the same character cannot be detected in Pb (1− x ) Ba x ZrO 3 bulk ceramics with Ba 2+ substitution at x < 0.3 . This difference can be attributed to the mismatch effect between the film and substrate and the smaller grain size . Although the dielectric permittivity (ε m ~ 1650 at 100 Hz) is higher compared with those found in PZT‐based compositions, it is rather lower than that obtained in corresponding sintered bulk PBZ ceramics with the same composition (ε m ~ 12000), which may most probably be due to the limited film thickness.…”

Ultrawideband dielectric spectroscopy of BaZrxTi1−xO3 ceramics and its microscopic mechanism of polarization

“…22 The contribution of dipole fluctuations in PNRs to the dipole polarization increases with increasing the volume fraction of PNRs, while the relaxation frequency of dipole polarization decreases with increasing the volume fraction of PNRs. 18,[23][24][25] The increase in dipole and the decrease in the relaxation frequency observed in Figs. 3 and 6 could be interpreted as increase of the volume fraction of PNRs with decreasing temperature.…”