Gobwute Rujijanagul

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...

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 .

Lead-free ternary perovskite compounds with large electromechanical strains

Lead-free compounds based on perovskite solid solutions in the ternary system (Bi1/2Na1/2)TiO3–(Bi1/2K1/2)TiO3–Bi(X1/2Ti1/2)O3, where X = Ni and Mg have been shown to exhibit large electromechanical strains. While the perovskite end members Bi(Mg1/2Ti1/2)O3 and Bi(Ni1/2Ti1/2)O3 display limited stability in their pure state, both compounds were found to have solid solubilities of at least 50 mol. % with (Bi1/2Na1/2)TiO3 and (Bi1/2K1/2)TiO3. Most importantly, under relatively large applied fields, these materials exhibited large hysteretic electromechanical strains characterized by a parabolic shape. With effective piezoelectric coefficients (d33*) greater than 500 pm/V, these systems have excellent potential as a Pb-free piezoelectric materials.

Relaxor behaviour of K0.5Bi0.5TiO3-BiScO3 ceramics

Dielectric properties of (1 − x)K0.5Bi0.5TiO3 − xBiScO3 ceramics have been studied for compositions x ≤ 0.5. Single-phase solid solutions occurred for compositions x < 0.25. A frequency-dependent dielectric relaxation was observed, consistent with relaxor behaviour. This gave rise to a relatively stable dielectric permittivity at high temperatures, for example, ɛr = 2880% ± 3%, between temperatures of 500 and 700 K (1 kHz) for composition x = 0.15. This consistency in relative permittivity occurs at higher temperatures than for other lead-free dielectrics. Parameters from Vogel-Fulcher analysis are compared to other relaxors.

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.

Improvement in dielectric and mechanical performance of CaCu3.1Ti4O12.1 by addition of Al2O3 nanoparticles

The properties of CaCu3.1Ti4O12.1 [CC3.1TO] ceramics with the addition of Al2O3 nanoparticles, prepared via a solid-state reaction technique, were investigated. The nanoparticle additive was found to inhibit grain growth with the average grain size decreasing from approximately 7.5 μm for CC3.1TO to approximately 2.0 μm for the unmodified samples, while the Knoop hardness value was found to improve with a maximum value of 9.8 GPa for the 1 vol.% Al2O3 sample. A very high dielectric constant > 60,000 with a low loss tangent (approximately 0.09) was observed for the 0.5 vol.% Al2O3 sample at 1 kHz and at room temperature. These data suggest that nanocomposites have a great potential for dielectric applications.

Effects of NiO nanoparticles on the magnetic properties and diffuse phase transition of BZT/NiO composites

A new composite system, Ba(Zr0.07Ti0.93)O3 (BZT93) ceramic/NiO nanoparticles, was fabricated to investigate the effect of NiO nanoparticles on the properties of these composites. M-H hysteresis loops showed an improvement in the magnetic behavior for higher NiO content samples plus modified ferroelectric properties. However, the 1 vol.% samples showed the optimum ferroelectric and ferromagnetic properties. Examination of the dielectric spectra showed that the NiO additive promoted a diffuse phase transition, and the two phase transition temperatures, as observed for BZT93, merged into a single phase transition temperature for the composite samples.

Morphotropic Phase Boundary of Lead-Free Piezoelectric Ceramics from BNT- KN System

In this research work, the investigation of the morphotropic phase boundary, physical properties and electrical properties of lead- free piezoelectric materials of bismuth sodium titanium oxide: (Bi0.5Na0.5)TiO3 (BNT) and potassium niobium oxide : KNbO3 (KN) in the ceramic system of (1-x)BNT- xKN where x= 0.00, 0.03, 0.05, 0.08, 0.10 and 0.15 by modified mixed oxide method was carried out. The BNT and KN powders were prepared separately using calcination technique with optimum calcination temperature for producing both BNT and KN powders of about 800°C. XRD results revealed that the BNT-KN ceramics with low KN content of x less than 0.05 contain ferroelectric perovskite phase with rhombohedral symmetries while the higher KN content ceramics have mixed symmetries between rhombohedral and orthorhombic. From the evidences including phases, microstructures and dielectric data of the BNT-KN ceramics, it may be assumed that the morphotropic phase boundary may be at around the composition of x = 0.05.

Effect of Carbon Addition on Dielectric Properties of 0-3 PZT-Portland Cement Composite

The dielectric properties of the 0-3 lead zirconate titanate (PZT)-portland cement (PC) composite with carbon addition were investigated. Lead zirconate titanate (PZT), Portland cement (PC) composite and carbon powder were fabricated using 50% of PZT, and varying addition of carbon 1, 2 % by volume. The dielectric properties were measured under room temperature at different frequency from 1kHz-20kHz. Carbon addition was found to slightly increase the dielectric constant of PZT-PC composite at room temperature. The results also show that both the carbon powder addition and frequency affected the dielectric constant and dielectric loss tangent of 0-3 all PZT-PC composites.

Observation of high dielectric constants in x(Pb(Zn1∕3Nb2∕3)O3–(0.2−x)Pb(Ni1∕3Nb2∕3)O3–0.8Pb(Zr1∕2Ti1∕2)O3 ternary solid solutions

In the present work, we demonstrate the results of combining two excellent ferroelectric materials at their morphotropic phase boundary compositions, i.e., 0.2(Pb(Zn1∕3Nb2∕3)O3–0.8Pb(Zr1∕2Ti1∕2)O3 (0.2PZN-0.8PZT) and 0.2Pb(Ni1∕3Nb2∕3)O3–0.8Pb(Zr1∕2Ti1∕2)O3 (0.2PNN-0.8PZT) to form a ternary solid solution of x(Pb(Zn1∕3Nb2∕3)O3–(0.2−x)Pb(Ni1∕3Nb2∕3)O3–0.8Pb(Zr1∕2Ti1∕2)O3 (xPZN-(0.2−x)PNN-0.8PZT) which exhibits superior dielectric properties. Examination of the dielectric spectra indicated that the ternary system exhibits a very high relative permittivity of 49 800 (at 10kHz) for the composition at x=0.10. In addition, an increased amount of PZN was observed to enhance the ferroelectric properties of the system.