Kyung Shin Koh

Phase diagram of pseudobinary Pb(Yb1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3 ceramic solid solution

Crystal structure and dielectric properties of (1−x)Pb(Yb1∕2Nb1∕2)O3−xPb(Sc1∕2Nb1∕2)O3 (PYN1−xPSNx) (0⩽x⩽0.60) solid solution have been studied, and its pseudobinary phase diagram has been determined. The low-temperature crystal structure of PYN1−xPSNx becomes pseudocubic from the PYN’s orthothombic with increasing x. Also the x-ray diffraction line intensities ascribed, respectively, to the antiferroelectric (AFE) lattice modulation and the B-site ordering become gradually weaker and then they disappear altogether for x>0.37. In the PYN-rich composition range (0⩽x<0.37), the paraelectric (PE)-AFE phase transition occurs sharply and its transition temperature remains independent of the applied frequency. However, on further increasing Sc concentration (0.37<x⩽0.60), the dielectric constant versus temperature curve becomes gradually broader and displays a frequency-dependent ferroelectric (FE) relaxor behavior. Particularly near x=0.37, the frequency-dependent dielectric behavior near the dielectric maximu...

Phase Transition Behavior of Sc-Substituted Pb(Yb 1/2 Nb 1/2 )O 3 Ceramics

The crystal structure and the dielectric properties of (1 m x )Pb(Yb 1/2 Nb 1/2 )O 3 m x Pb(Sc 1/2 Nb 1/2 )O 3 (PYN 1 m x PSN x ) (0 h x h 0.50) solid solution have been studied. According to the XRD study, the room temperature crystal structure of PYN 1 m x PSN x becomes pseudocubic from the PYNs orthothombic with increasing x . Also the diffraction line intensities ascribed respectively to the AFE lattice modulation and the B-site ordering become gradually weaker and they disappear altogether for x > 0.30. In the PYN-rich composition range (0 h x h 0.30), the paraelectric(PE)-antiferroelectric(AFE) phase transition occurs sharply and is independent of the applied frequency. However, on further increasing Sc concentration (0.30 < x h 0.50), the dielectric constant vs. temperature curve becomes gradually broader and begins to display the frequency-dependent relaxor behavior.

Structural and Dielectric Behavior or Ba-Substituted Pb(Yb 1/2 Nb 1/2 )O 3 Ceramics

The crystal structure and the dielectric properties of the antiferroelectric solid solution of (1 m x )Pb(Yb 1/2 Nb 1/2 )O 3 m x Ba(Yb 1/2 Nb 1/2 )O 3 (Pb 1 m x Ba x YN) (0 h x h 0.30) have been studied. The crystal structure is shown to become pseudocubic from the PYNs orthorhombic structure on solutionizing for x >0.5 while the transition shows a normal first-order paraelectric(PE) - antiferroelectric(AFE) behavior increasing x < 0.14. The transition temperature gradually decreases with the increasing Ba 2+ concentration. In the composition range 0.16 x 0.30, a typical relaxor behavior is displayed.

Preparation and Electrical Properties of Sol-Gel Derived (1 − x)Pb(Zn1/3Nb2/3)O3-xPb(Zr0.4Ti0.6)O3(x = 0.6) Thin Films

Abstract Films of (1− x)Pb(Zn1/3Nb2/3)O3- xPb(Zr0.4Ti0.6)O3 ( x = 0.6, 40 PZN-60PZT) were deposited on Pt/TiO2/SiO2/Si substrate through spin coating. Using a combination of homogeneous precursor solutions and two-step pyrolysis process, it was possible to obtain the 40PZN-60PZT thin films of perovskite phase virtually without pyrochlore phase precipitation after annealing above 650°C. The root-mean-square surface roughness of a 220 nm thick film was 3 nm as measured by the atomic force microscopy. The 40PZN-60PZT films annealed at 720°C showed a well-saturated hysteresis loop at an applied voltage of 5 V with remanent polarization ( P r ) and coercive voltage ( V c ) of 29 μ C/cm2 and 0.8 V, respectively. The leakage current density was lower than 10− 6A/cm2 at an applied voltage of 2.5 V.

Annealing Temperature Effect of PbZr0.4Ti0.6O3 Film on La1/2Sr1/2CoO3 Bottom Electrode

We have investigated the ferroelectric and electrical properties of PZT 40/60 films on the bottom La1/2Sr1/2CoO3(LSCO) electrode. The LSCO bottom electrode was sputtered on the SiO2/Si(100). As the annealing temperature of PZT capacitors on the LSCO is increased, the ferroelectric properties gradually increase with the annealing temperature up to 650°C. However, for the PZT capacitors annealed above 650°C, electrical measurement cannot be performed.

Preparation of B-Site Ordered Complex Perovskite SrYb 0.5 Nb 0.5 O 3 by Amorphous Citrate Process

Amorphous citrate process has been used to synthesize the complex perovskite SrYb 0.5 Nb 0.5 O 3 (SYN) powder. Citrate-nitrate gels were produced at room temperature by first reacting NbCl 5 with aqueous solution of NH 4 OH to produce Nb(OH) 5 and then mixing the filtered Nb(OH) 5 with strontium nitrate and yitterbium nitrate in citric acid aqueous solution. The precursor ash was produced by auto ignition of the dehydrated precursor gel at 200°C. Finely crystallized SYN powder could be obtained by thermal decomposition of the citrate precursors ash at temperature as low as 1000°C. X-ray diffraction, Infra-red transmittance spectroscopy and electron microscopy have been used to characterize the precursors and annealed materials synthesized by citrate process. The citrate process is very promising and simple for preparing complex perovskite SrYb 0.5 Nb 0.5 O 3 .

Thermomechanical behaviors and antiferroelectric superstructures in Pb(Yb1/2Nb1/2)O3–rich Pb(Yb1/2Nb1/2)O3–Pb(Fe1/2Nb1/2)O3 solution system

Abstract The phase transition behavior of the pseudo-binary (1-x Pb(Yb1/2Nb1/2)O3–xPb(Fe1/2Nb1/2)O3 solid solution has been investigated by thermal expansion and x-ray diffraction. The deviation from the high temperature thermal expansion at temperature near the paraelectric-antiferoelectric (ferroelectric) transition can be explained by the elastic strain coupling to the dipole moments via the electrostriction. For 0<x<0.11, the transition is characteristically sharp, whereas for 0.14≤x≤0.3 it is diffise. X-ray diffraction of pure Pb(Ybl/2Nb1/2)O3 shows a well-defined antiferroelectric superstructure. With the increasing Pb(Fe1/2Nb1/2)O3 concentration, the order-disorder as well as displacement superstructure is observed to diminish. Such structural manifestation on transition seems to be connected with the dielectric behavior.