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Zhai, Jiwei,Chen, Haydn The Korean Ceramic Society 2003 한국세라믹학회지 Vol.40 No.4
The effects of the mole concentrations of precursor solution on the microstructure and dielectric properties of sol-gel deposited $Ba_{0.85}$S $r_{0.15}$Ti $O_3$(BST) thin films have been investigated. The films were of single perovskite phase with strong (100) preferred orientation when grown on LaNi0$_3$ buffered Pt/Ti/ $SiO_2$Si substrates using a diluted precursor solution. Variation of the precursor solution concentration resulted in a different microstructure and, in turn, affected the tunability of the sol-gel deposited films. It was observed that leakage currents increased asymmetrically for the negative and positive bias voltage with decreasing thickness. Overall results suggest that those BST films have acceptable properties f3r applications as room-temperature tunable elements.
Xing Liu,Jiwei Zhai,Bo Shen,Feng Li,Yang Zhang,Peng Li,Baihui Liu 한국물리학회 2017 Current Applied Physics Vol.17 No.5
In this work, the temperature-induced structural evolution in 0.79(Na0.5Bi0.5)TiO3-0.2(K0.5Bi0.5)TiO3- 0.01(K0.5Na0.5)NbO3 (NKBNT) lead-free ceramics was investigated by Raman microscopic spectroscopy combined with electrical macroscopic measurements. The NKBNT ceramics possess the local structure with the coexisted rhombohedral R3c and tetragonal P4bm polar-nano-regions (PNRs). The R3c and P4bm PNRs coexist in a wide temperature range, then the local structure transforms to the P4bm PNRs around the temperature of dielectric maximum (Tm) evidenced by the doublet splitting of Ti-O modes (peak B) and oxygen octahedral vibrational modes (peak C). The discontinuous changes of wavenumber and linewidth of peak B2 and peak C3 as well as the dielectric local maxima around the rhombohedral-tetragonal phase transition temperature (TRT) are considered to result from the thermal evolution of R3c and P4bm PNRs. The macroscopic changes of non-polar phase with electric field and temperature were investigated by the temperature-dependent polarization-electric field (P-E) loops, current-electric field (I-E) loops and bipolar strain (S-E) curves. The electric-field level necessary to form the long-range ferroelectric order from non-polar phase associated with the stability of the induced ferroelectric phase depends strongly on the temperature.
Wei Li,Jigong Hao,Huarong Zeng,Jiwei Zhai 한국물리학회 2013 Current Applied Physics Vol.13 No.7
Lead free Ba0.92Ca0.08Ti0.95Zr0.05O3 (BCZT) thin films were deposited on Pt/Ti/SiO2/Si and LaNiO3(LNO)/Pt/Ti/SiO2/Si substrates by a solegel processing technique, respectively. The effects of substrate on structure,dielectric and piezoelectric properties were investigated in detail. The BCZT thin films deposited on LNO/Pt/Ti/SiO2/Si substrates exhibit (100) orientation, larger grain size and higher dielectric tunability (64%). The BCZT thin films deposited on Pt/Ti/SiO2/Si exhibit (110) orientation, higher Curie temperature (75 ℃),better piezoelectric property (d33 of 50 pm/V) and lower dielectric loss (0.02). The differences in dielectric and piezoelectric properties in the two kinds of oriented BCZT films should be attributed to the difference of structure, in-plane stress and polarization rotation in orientation engineered BCZT films.
Yuze Xue,Mingwei Zhang,Le Xin,Luchao Ren,Panpan Lv,Hang Zhan,Jing He,Jiwei Zhai 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.2
0.2ZnAl2O4/0.8Ba0.5Sr0.5TiO3 ceramics with good dielectric temperature stability were synthesized by controlling sinteringbehavior. The relationship between sintering conditions, microstructure, and dielectric properties of ceramics was studied. Cubic structures were confirmed in all ceramics. Double sintering (DS) behavior can effectively improve the density, and thegrain size has no obvious change compared with non-repeated sintering. The maximum dielectric permittivity (220 at 10 kHz)and minimum leakage current (3.98×10-6 A/cm2 at 0.25 kV/cm) are obtained in the DS ceramics, which is superior to thoseof the single sintering ceramics. This can be ascribed to the higher relative density of the DS ceramics in contrast to the singlesintering ceramics. More importantly, the temperature stability of the DS sample in all samples is optimal due to the highsurface energy at grain boundaries and improved density. This work demonstrates a route to produce ceramics with weaktemperature sensitivity for microwave applications.