Page 104 - Read Online

Wang et al. Microstructures 2023;3:2023023 https://dx.doi.org/10.20517/microstructures.2023.04 Page 3 of 10

will be improved due to the enhanced relaxation property and breakdown electric field.

MATERIALS AND METHODS
Ceramic samples of (1-x)[0.94Bi Na TiO -0.06BaTiO ]-xSr Biγ Ti Zr O (abbreviated as: (1-x)BNBT-
0.8
0.95
0.2
0.1
3
0.5
0.5
0.8
3
xSBTZ, x = 0.07, 0.08, 0.09, and 0.10) were synthesized using the solid-state reaction method. The starting
materials used were Bi O (99.9%), Na CO (99.5%), BaCO (99.9%), SrCO (99%), TiO (99.6%), and ZrO
2
3
2
3
2
3
2
3
(99.99%). The raw powders were mixed and ball-milled for 16 h in polyethylene pots with zirconia balls and
ethanol as the milling medium. The use of ethanol was preferred due to its low ion dissolution properties,
which minimized the introduction of unwanted ions. The milled powder was dried, sieved, and formed into
cylindrical pellets before being sintered for 4 h at 850 °C The sintered pellets were then crushed, re-milled
for 10 h, and cold isostatically pressed into pellets with a diameter of 10 mm under a pressure of 250 MPa.
The pellets were sintered at 1150 °C for 2 h in alumina crucibles in an air atmosphere. To compensate for
the loss of sodium oxides and bismuth, the pellets were buried in prepared powders of the same
composition. Finally, the sintered pellets were polished to a final thickness of approximately 0.6 mm, and
silver electrodes were coated on both surfaces and fired at 550 °C for 30 min for electrical testing.
The phase structure was determined through the use of X-ray diffractometry (XRD, Advanced), while the
surface morphology was analyzed by means of scanning electron microscopy (SEM) (Carle Zeiss
GeminiSEM 500, Germany). In addition, the dielectric properties were measured using a precision
impedance analyzer (Agilent E4980A), while Raman spectra were obtained using a Raman spectrometer
(Horiba Allmentation LabRam). Finally, the polarization hysteresis loops (P-E) were assessed via a standard
ferroelectric analyzer (TF Analyzer 2000).
RESULTS AND DISCUSSION
The X-ray diffraction patterns of BNBT-xSBTZ ceramics were analyzed in the range of 20° to 75°, as shown
in Figure 1A. The results indicate that each sample has a single perovskite structure, with no presence of any
secondary phase. This suggests that SBTZ is fully incorporated into the lattice . Furthermore, Figure 1B
[13]
displays the expanded XRD patterns around the diffraction peak of (111), which reveals that the diffraction
peaks shift towards higher diffraction angles as the SBTZ doping content increases. This shift indicates a
reduction in the lattice constant [14,15] . Additionally, the absence of peak splitting at around 40° suggests that
[16]
all samples possess a highly symmetrical pseudocubic structure .
The Raman spectra of (1-x)BNBT-xSBTZ ceramics were analyzed in the range of 100-1,000 cm , as depicted
-1
in Figure 1C. The spectra were categorized into four regions, each representing distinct chemical bonding
behavior . The modes below 200 cm were found to be associated with A-site atomic vibrations, while the
[17]
-1
-1
high-frequency band between 200 and 380 cm corresponded to the vibrations of BO bonds, including Zr ,
2+
Zr , and Ti ions. The modes near 550 cm and 610 cm were linked to Ti/Zr-O vibrations, and it was
-1
-1
4+
4+
6
observed that the two peak positions became separated, indicating an increased intensity of oxygen
[18]
octahedron vibration and enhanced relaxation characteristics with increasing doping content . The section
with modes above 700 cm was considered to be the superposition of various vibration modes.
-1
The SEM images of (1-x)BNBT-xSBTZ ceramics, as depicted in Figure 2A-D, indicate that the ceramics
have been effectively sintered with minimal surface pores. The grain size of the ceramics initially decreases
and then increases with increasing dopant concentration. This phenomenon can be attributed to the
appearance of low melting point regions in the ceramics after SBTZ doping. During the sintering and
cooling process, these regions are more prone to nucleation and grain growth, resulting in a decrease in
grain size. However, at higher doping concentrations, the liquid phase melting regions further increase,