Naratip Vittayakorn

The morphotropic phase boundary and dielectric properties of the xPb(Zr1∕2Ti1∕2)O3-(1−x)Pb(Ni1∕3Nb2∕3)O3 perovskite solid solution

The solid solution between the normal ferroelectric Pb(Zr1∕2Ti1∕2)O3 (PZT) and relaxor ferroelectric Pb(Ni1∕3Nb2∕3)O3 (PNN) was synthesized by the columbite method. The phase structure and dielectric properties of xPZT-(1−x)PNN where x=0.4–0.9 and the Zr∕Ti composition was fixed close to the morphotropic phase boundary (MPB) were investigated. With these data, the ferroelectric phase diagram between PZT and PNN has been established. The relaxor ferroelectric nature of PNN gradually transformed towards a normal ferroelectric state towards the composition 0.7PZT-0.3PNN, in which the permittivity was characterized by a sharp peak and the disappearance of dispersive behavior. X-ray diffraction analysis demonstrated the coexistence of both the rhombohedral and tetragonal phases at the composition 0.8PZT-0.2PNN, a new morphotropic phase boundary within this system. Examination of the dielectric spectra indicates that PZT-PNN exhibits an extremely high relative permittivity near the MPB composition. The permitti...

Phase transitions and ferroelectric properties in BiScO3-Bi(Zn1∕2Ti1∕2)O3-BaTiO3 solid solutions

Ceramics solid solutions within the ternary perovskite system Bi(Zn1∕2Ti1∕2)O3-BiScO3-BaTiO3 were synthesized via solid-state processing techniques. The crystal structure of sintered ceramics was analyzed by x-ray diffraction. A stable perovskite phase was obtained for all compositions with a BaTiO3 content greater than 50 mol %. Furthermore, a change in symmetry from pseudocubic to tetragonal was observed as the mole fraction of BaTiO3 increased. Dielectric measurements show a dielectric anomaly associated with a phase transformation over the temperature range of 30 °C–210 °C for all compositions. Examination of the polarization hysteresis behavior revealed weakly nonlinear hysteresis loops. With these data, ferroelectric phase diagrams were derived showing the transition between the pseudocubic relaxor behavior to the tetragonal normal ferroelectric behavior. This transition was also correlated with changes in the diffuseness parameter.

Perovskite phase formation and ferroelectric properties of the lead nickel niobate-lead zinc niobate-lead zirconate titanate ternary system

The ternary system of lead nickel niobate Pb(Ni 1 / 3 Nb 2 / 3 )O 3 (PNN), lead zinc niobate Pb(Zn 1 / 3 Nb 2 / 3 )O 3 (PZN), and lead zirconate titanate Pb(Zr 1 / 2 Ti 1 / 2 )O 3 (PZT) was investigated to determine the influence of different solid state processing conditions on dielectric and ferroelectric properties. The ceramic materials were characterized using x-ray diffraction, dielectric measurements, and hysteresis measurements. To stabilize the perovskite phase, the columbite route was utilized with a double crucible technique and excess PbO. The phase-pure perovskite phase of PNN-PZN-PZT ceramics was obtained over a wide compositional range. It was observed that for the ternary system 0.5PNN-(0.5- x)PZN-xPZT, the change in the transition temperature (T m ) is approximately linear with respect to the PZT content in the range x = 0 to 0.5. With an increase in x, T m shifts up to high temperatures. Examination of the remanent polarization (P r ) revealed a significant increase with increasing x. In addition, the relative permittivity (∈ r ) increased as a function of x. The highest permittivities (∈ r = 22,000) and the highest remanent polarization (P r = 25 μC/cm 2 ) were recorded for the binary composition 0.5Pb(Ni 1 / 3 Nb 2 / 3 )O 3 -0.5Pb(Zr 1 / 2 Ti 1 / 2 )O 3 .

Non-isothermal kinetics of the thermal decomposition of sodium oxalate Na2C2O4

The thermal transformation of Na2C2O4 was studied in N2 atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na2C2O4 and its decomposed product were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique (XRD). The non-isothermal kinetic of the decomposition was studied by the mean of Ozawa and Kissinger–Akahira–Sunose (KAS) methods. The activation energies (Eα) of Na2C2O4 decomposition were found to be consistent. Decreasing Eα at increased decomposition temperature indicated the multi-step nature of the process. The possible conversion function estimated through the Liqing–Donghua method was ‘cylindrical symmetry (R2 or F1/2)’ of the phase boundary mechanism. Thermodynamic functions (ΔH*, ΔG* and ΔS*), calculated by the Activated complex theory and kinetic parameters, indicated that the decomposition step is a high energy pathway and revealed a very hard mechanism.

THE STRUCTURAL PHASE AND MICROSTRUCTURES OF PEROVSKITE Ba(Ti1-xZrx)O3 CERAMICS USING THE COMBUSTION ROUTE

Ba(Ti1-xZrx)O3; BTZ (x = 0.20 and 0.25) ceramics are attractive candidates for dynamic random access memories, tunable microwave devices and capacitors. In this study, the preparation of BTZ powders and ceramics fabricated by the combustion method were studied in detail. The calcination and sintering conditions were performed from 600 to 900°C for 4 h and from 1300 to 1450°C for 2 h, respectively. The highest percentage of the cubic perovskite phase was found in the powders that were calcined at 800°C. A pure cubic perovskite structure was found in all ceramic samples. The average grain size increased with increasing sintering temperatures. Dielectric constant-temperature plots showed a maximum peak value of 7500 and 8300 for x = 0.20 and 0.25. The phase transition temperature of the BTZ ceramics occurred at 30°C and 10°C for x = 20 and 25, respectively.

Physical properties and phase transitions in perovskite Pb[Zr1−x(Ni1/3Nb2/3)x]O3 (0.0 ⩽ x ⩽ 0.5) ceramics

A solid solution of lead zirconate–lead nickel niobate ceramics, Pb[Zr1−x(Ni1/3Nb2/3)x]O3 (PZNN) with x = 0.0–0.5, was synthesized via the columbite precursor method. The crystal structures as well as the thermal and dielectric properties were investigated in terms of the lead nickel niobate (PNN) concentration. X-ray diffraction indicated that all samples exhibited a single-phase perovskite structure. At room temperature, Pb[Zr1−x(Ni1/3Nb2/3)x]O3 is orthorhombic for a composition where x = 0, rhombohedral for the compositions where x = 0.1, 0.2 and 0.3 and pseudo-cubic for compositions where x = 0.4 and 0.5. The results of the addition of lead nickel niobate to the lead zirconate ceramic showed enhancement of the room-temperature dielectric permittivity. Lead nickel niobate substitution also led to lower transition temperatures. Furthermore, this transition from normal to relaxor FE ceramics was typified by a quasi-linear relationship between the diffuseness parameter δγ and the PNN mole fraction x.

Structure and ferroelectric properties of Bi(Zn 1/2 Ti 1/2 )O 3 -(Bi 1/2 K 1/2 )TiO 3 perovskite solid solutions

Lead-free piezoelectric ceramics based on chiBi(Zn_1/2Ti_1/2)O₃-(1-chi)(Bi_1/2K_1/2)TiO₃ were obtained via solid state processing techniques. A single perovskite phase with tetragonal symmetry was obtained for Bi(Zn_1/2Ti_1/2)O₃ (BZT) substitutions up to 20 mol%. The maximum density was 97.1% at the composition of chi = 0.1. The dielectric measurement indicated that the transition temperature decreased linearly with increasing BZT content. The P-E loops revealed an increase in remanent polarization (P_r) with the addition of BZT. The maximum planar coupling coefficient, kappa_r, for the chi = 0.1 composition was 21.6 and the piezoelectric coefficient, d₃₃, for chi = 0, chi = 0.05, and chi = 0.1 was 108, 185, and 235 pm/V, respectively. Overall, the dielectric and piezoelectric properties showed significant improvement when BZT was added.

Dielectric and ferroelectric characteristics of 0.7PZT-0.3PZN ceramics substituted with Sr

Lead zirconate titanate–lead zinc niobate (PZT–PZN) ceramics with compositions close to the morphotropic phase boundary were investigated as a function of Sr doping. The powders were prepared using the columbite-(wolframite) precursor method. Dielectric and ferroelectric properties of the as-sintered and annealed samples were measured. The results showed that with increasing Sr concentration dielectric constant versus temperature curves become gradually broader. Sr doping has been shown to produce a linear reduction in the transition temperature (Tm) (294.1−12.7x °C) with concentration (x). The maximum value of the dielectric constant decreased and the degree of diffuse phase transition was enhanced with Sr doping. However, the results indicated that the degree of disorder in Sr-modified PZT–PZN was further improved by thermal annealing. After thermal annealing at 900°C for 48 h a strong enhancement of dielectric constant (er) and remanent polarization (Pr) was observed.

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.

Dielectric properties and phase transition behaviors in (1−x)PbZrO3–xPb(Mg1/2W1/2)O3 ceramics

The solid solution of lead zirconate [PbZrO3 (PZ)] and lead magnesium tungstate [Pb(Mg1/2W1/2)O3 (PMW)] has been synthesized by the wolframite precursor method. The crystal structure, phase transformations, dielectric and thermal properties of (1−x)PZ-xPMW, where x=0.00–0.10, were investigated. The crystal structure of sintered ceramics was analyzed by x-ray diffraction. Phase-pure perovskite was obtained for all compositions. Furthermore, a change from orthorhombic to rhombohedral symmetry was observed as the mole fraction of increased PMW. As a result, it was found that PbZrO3–Pb(Mg1/2W1/2)O3 undergoes successive transitions from the antiferroelectric phase to the ferroelectric phase to the paraelectric state. The coexistence of orthorhombic and rhombohedral phases in this binary system is located near the composition x=0.1.