Order–disorder behavior in Ba(Zn1/3Ta2/3)O3

Abstract

Sintered (1475 °C/2 h) pellets of Ba(Zn1/3Ta2/3)O3 were annealed at temperatures ranging from 1550 to 1625 °C/15 h and subsequently quenched into water. The degree of B-site order between the Zn and Ta cations was investigated using x-ray diffraction (XRD) and transmission electron microscopy (TEM). Samples quenched from 1575 to 1600 °C exhibit the highest degree of order by XRD. Dark-field TEM images from these samples revealed 1:2, Zn:Ta, trigonal, ordered domains approximately 0.4 μm diam near grain boundaries but 100 nm in the grain interior. Samples annealed and quenched from 1625 °C exhibited no ordered superlattice reflections by XRD. However, diffuse scatter along 〈111〉 directions and fcc rather than trigonal ordered reflections were observed in electron diffraction patterns. Disordered samples were subsequently annealed at 1500 °C/15 h (below the order–disorder phase transition ∼1625 °C) and ±13{hkl} superlattice reflections reappeared in XRD patterns demonstrating the reversibility of the phase transition.

Microwave properties of Ba(Zn1/3Ta2/3)O3 dielectric resonators

“…4c indicates a bimodal grain size distribution, with small grains near 2 m and bigger ones near 6-7 m. The intergrain porosity is small, only pores with size in the interval 0.5-2 m are present. Well faceted, polyhedral grains with smooth surfaces and edges showing dimensions in the range (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) m are observed for BZT sample sintered at 1650 • C (Fig. 4d).…”

“…Gallasso and Pyle [15] concluded that the B-site ordering increased as the difference in charge and size between B and B atoms increased. Reaney et al [16,17] studied the order-disorder transition in BZT using XRD and TEM. They found that the reversible order-disorder phase transition in BZT occurs between 1600 and 1625 • C. The cation ordering in Ba(Zn 1/3 Ta 2/3 )O 3 complex perovskite is important because the 1:2 ordering along 1 1 1 direction is closely related to the high-Q property of BZT.…”

Phase microstructure evaluation and microwave dielectric properties of (1–x)Mg0.95Ni0.05Ti0.98Zr0.02O3–xCa0.6La0.8/3TiO3 ceramics

“…Ba(Zn 1/3 Ta 2/3 )O 3 and Ba(Mg 1/3 Ta 2/3 )O 3 showed the highest values ( is the unloaded quality factor and u 0 Q f 0 u Q f is the resonant frequency) ranging from 100000 to about 200000 GHz among these materials [8,9]. However, these contain Ta which is very costly.…”

“…However, these contain Ta which is very costly. Moreover, these require high sintering temperature (1600 to 1650 ℃) and long soaking time (~50 h) for achieving optimum densities that also contribute to the high cost of preparation of these materials [8,9]. Therefore, Ta free materials with low sintering temperature are urgently desired for high frequency applications.…”

Structural, chemical and dielectric properties of ceramic injection moulded Ba(Zn1/3Ta2/3)O3 microwave dielectric ceramics

“…18,19 For example in ABO 3 perovskites, τ f can be directly correlated to the nature and extent of B-site ordering, as reported in a study of Ba x Sr 1−x (Zn 1/3 Nb 2/3 )O 3 . 20 As the order-disorder transition in Ba(Zn 1/3 Ta 2/3 )O 3 (1500-1625 • C) 21 falls in the range of the sintering temperatures used in our study, the changes in τ f with sintering temperature may be attributed to variation in the type and extent of ordering. Note that large changes in the degree of ordering as monitored by X-ray diffraction in our study were not found.…”