Anurak Prasatkhetragarn

Synthesis and Dielectric and Ferroelectric Properties of Ceramics in (1-x)Pb(Zr1/2Ti1/2)O3?(x)Pb(Co1/3Nb2/3)O3 System

Ceramics in a PZT–PCN system with the formula (1-x)Pb(Zr1/2Ti1/2)O3–(x)Pb(Co1/3Nb2/3)O3, where x = 0.1–0.5, were prepared using a solid-state mixed-oxide technique (the columbite-wolframite precursor method). The phase formation behavior and microstructure were studied using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM), respectively. The dielectric and ferroelectric properties of the compounds were studied and discussed. Phase-pure perovskites of PZT–PCN ceramics were obtained over a wide compositional range. In addition, the XRD, dielectric, and ferroelectric properties confirmed that the morphotropic phase boundary (MPB) composition between the tetragonal and pseudo cubic phases of this system lied between 0.2 ≤x ≤0.3.

Effect of calcination conditions on phase formation and particle size of Zn3Nb2O8 powders synthesized by solid-state reaction

Abstract The solid-state mixed oxide method via a rapid vibro-milling technique is explored in the preparation of single-phase Zn 3 Nb 2 O 8 powders. The formation of the Zn 3 Nb 2 O 8 phase in the calcined powders has been investigated as a function of calcination conditions by TG–DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. It has been found that the minor phases of unreacted ZnO and Nb 2 O 5 precursors and the columbite ZnNb 2 O 6 phase tend to form together with the Zn 3 Nb 2 O 8 phase, depending on calcination conditions. It is seen that optimization of calcination conditions can lead to a single-phase Zn 3 Nb 2 O 8 in a monoclinic phase.

Structure and electrical properties of double perovskite Sr(Ni1/2Mo1/2)O3 ceramics

The double perovskite Sr(Ni1∕2Mo1∕2)O3 has been prepared with solid-state reaction and was characterized by x-ray diffraction technique. It has been indicated that the single phase is formed at 1300°C in air. The compound undergoes a phase transition at 280°C, where the structure of the ordered perovskite type changes from tetragonal (I4∕m) to cubic (Fm3¯m). Dielectric constant (er) and dielectric loss (tanδ) are observed at the transition point. The conductivity of the sample has been studied, and the slope of dc conductivity versus the inverse of temperature corresponds to an Arrhenius activation energy in the range of 0.34–0.46eV. This range of activation is nearly double ionized oxygen vacancies VO⋅⋅ in the resistivity transition of other perovskite oxides.

Phase Transitions and Dielectric Properties in Bi(Zn1/2Ti1/2)O3–(Na1-yLiy)NbO3 Perovskite Solid Solutions

Perovskite solid solutions based on the system Bi(Zn1/2Ti1/2)O3–NaNbO3 were obtained via solid-state processing techniques. The crystal structure and ferroelectric phase transitions were studied by means of X-ray diffraction and dielectric measurements. A stable perovskite phase was obtained for Bi(Zn1/2Ti1/2)O3 substitutions up to 10 mol %. The dielectric characterization revealed that as the Bi(Zn1/2Ti1/2)O3 content increased, the transition temperature decreased and the transition peak became very diffuse. The polarization hysteresis loop and strain measurements presented evidence of an induced ferroelectric phase with 1 mol % Bi(Zn1/2Ti1/2)O3 substitutions. The planar coupling factor (kp) for 0.01Bi(Zn1/2Ti1/2)O3–0.99NaNbO3 was measured to be 0.28. In addition, with the substitution of Li for Na in the Bi(Zn1/2Ti1/2)O3–(Na1-yLiy)NbO3 system, the diffuseness of the transition peak decreased and the transition temperature increased.

Effects of vibro-milling time on phase formation and particle size of Zn3Nb2O8 nanopowders

Zinc niobate, ZnNb2O6, nanopowders was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of milling time on the phase formation and particle size of ZnNb2O6 powder was investigated. The formation of the ZnNb2O6 phase investigated as a function of calcination conditions by DTA and XRD. The particle size distribution of the calcined powders was determined by laser diffraction technique, while morphology, crystal structure and phase composition were determined via a SEM techniques. In addition, by employing an appropriate choice of milling time, a narrow particle size distribution curve was also observed.

Dielectric Aging of Cr-Doped PZT Ceramics

The aging of dielectric properties of Cr-Doped Pb(Zr0.52Ti0.48)O3 were investigated. The composition of Pb(Zr0.52Ti0.48)O3 with 0.1, 0.2, 0.4, 0.6, 1.0 and 3.0 mol% of Cr2O3 addition were prepared by conventional mixed oxide technique. The aging has been measured at room temperature after quenching from high temperatures above the Curie temperature. The dielectric aging of all compositions revealed relaxor aging behavior. The aging rate of stable stage obeyed a logarithmic time dependence, while the aging rate decreased with increasing Cr2O3 at low concentration (0.1–0.6). Further increase in Cr2O3 concentration, the aging rate turned to increase.

Electrical Conductivity and Dielectric and Ferroelectric Properties of Chromium Doped Lead Zirconate Titanate Ceramic

In this study, the influence of the addition of chromium (Cr 3+) of 0.1–3 mol% on electrical conductivity, dielectric and ferroelectric properties of the morphotropic lead zirconate titanate (Pb(Zr 0.52 Ti 0.48 )O 3 ) ceramics has been investigated. The dielectric constant tends to slightly increase with increasing chromium concentration from 0.1–0.6 mol% while dielectric loss tends to decrease, but the trend is reversed with 1–3 mol% chromium content. In addition, the Curie temperature (T C ) does not change significantly with chromium addition from 0.1–0.6 mol% but decreases significantly from 1–3 mol%. From the hysteresis loop measurement, at low concentration of Cr, the loops reveal the high value of polarization and low coercive field that refers to soft behavior while the contrary is revealed at higher Cr concentration with hard behavior. The electrical conductivity of the doped PZT ceramic measured at 50–200°C decreases with increasing chromium concentration from 0.1–0.6 mol% but increases with 1–3 mol% Cr.

Effect of Calcination Condition on Phase Formation of Zirconium Titanate Powders Synthesized by the Solid-State Reaction

Zirconium titanate (ZrTiO 4 ; ZT) powders have been prepared by using a solid-state reaction combined with a vibro-milling technique. The effects of calcination temperature, dwell time and heating/cooling rates on phase formation and morphology of the powders were examined. The calcination temperature and dwell time have been found to show a pronounced effect on the phase formation of the calcined zirconium titanate powders. Additionally, the minor phase of unreacted TiO 2 tends to form together with ZrTiO 4 , depending on calcination conditions. It is seen that optimization of calcination conditions can lead to 100% yield of an orthorhombic ZrTiO 4 .

Effect of Two-Stage Reaction Sintering Technique on Phase Formation, Microstructure and Dielectric Properties of 0.93Pb(Zn1/3Nb2/3)O3–0.07BaTiO3 Ceramics

Influences of a combination between the two-stage sintering and the reaction sintering techniques on phase formation, microstructure and dielectric properties of relaxor perovskite 0.93Pb(Zn1/3Nb2/3)O3–0.07BaTiO3 or 0.93PZN-0.07BT ceramics were determined via X-ray diffraction, scanning electron microscopy and dielectric measurement techniques, respectively. Under suitable two-stage reaction sintering schemes, it was found that dense and pure perovskite 0.93PZN-0.07BT ceramics with fine grain size can be successfully achieved with better dielectric properties than those of ceramics from single-stage reaction sintering.

Structural Investigation of PZT-PNN and PZT-PZN Probed by Synchrotron X-ray Absorption Spectroscopy

Relaxor ferroelectric materials PZT-PZN and PZT-PNN were prepared by columbite method. The structural change was investigated by Synchrotron X-ray Absorption Spectroscopy (SXAS) at Zr L3-edge. The results show structural change of both systems affects to white line (WL) intensity significantly as revealed by simulated spectra. At the MPB composition 0.7PZT-0.3PZN shows the enhance magnitude change as structure change from tetragonal to only rhombohedral phase. While the MPB composition 0.8PZT-0.2PNN shows the slight change of magnitude of WL intensity which mixed phases of rhombohedral and tetragonal. Therefore, the MPB composition of PZT-PNN system clearly conclude that is 0.7PZT-0.3PZN but the MPB of PZT-PNN system could not be conclude like that because the structure slightly change.