Abstract
The degree of Zn2+ and Ta5+ ions ordering could play an important role in the dielectric loss in Ba(Zn1/3Ta2/3)O3 (BZT) ceramics. However, the influence of the grain size of Ba(B′1/3B″2/3)O3 ceramics with nano or sub-micron grains on the ordering domains structure is still not clear. In the present paper, highly dense (~98%) BZT microwave dielectric ceramics with homogeneous sub-micron structure (~330 nm) were prepared through spark plasma sintering (SPS). High resolution transmission electron microscopy combined with X-ray diffraction (XRD)clearly showed that the B-site ordering structure of sintered BZT samples by SPS becomes the B-site long-range 1:2 ordering as annealing proceeds. In contrast, the short-range 1:2 ordering in non-annealed counterparts was also present, which was not detectable by XRD. The size of B-site ordering domains enlarged with annealing temperature. The sub-micron structure of sintered BZT ceramics by SPS remained stable at up to 1400 C; however, the size of B-site 1:2 ordering domain was more than five times larger, which led to a significant increase of the quality factor (Q·f) to 37,700 GHz from 15,000 GHz.
Highlights
Complex perovskite Ba(B0 1/3 B00 2/3 )O3 ceramics have become one of the most important microwave dielectric ceramics for wireless communication systems due to their very low dielectric loss or high quality factor (Q·f ), relatively high dielectric constant, and near-zero temperature coefficient of resonant frequency (τ f ) [1,2,3]
Using Ba(Zn1/3 Ta2/3 )O3 (BZT) ceramics with sub-micron structure as a prototype of Ba(B0 1/3 B00 2/3 )O3 ceramics, the present paper aimed to investigate the evolution of B-site ordering and ordering domains in sub-micron structured BZT ceramics fabricated by spark plasma sintering (SPS) during the annealing processing
The grain sizes of BZT samples rely on the sintering temperature
Summary
Complex perovskite Ba(B0 1/3 B00 2/3 )O3 ceramics have become one of the most important microwave dielectric ceramics for wireless communication systems due to their very low dielectric loss or high quality factor (Q·f ), relatively high dielectric constant (εr ), and near-zero temperature coefficient of resonant frequency (τ f ) [1,2,3]. Ba(Zn1/3 Ta2/3 )O3 (BZT) microwave ceramics, as dielectric resonators and filters, have been broadly utilized in the wireless technologies [4]. It has been accepted that the quality factor of BZT ceramics is relevant to the degree of B-site { . B-site 1:2 ordering degree, high annealing temperature (~1450 ◦ C) and long soaking time (~48 h) are necessary [13,14,15]. Tamura et al further showed that BaZrO3 doping significantly shortens necessary annealing time to obtain high Q·f values [16]. With the increasing doping amount of Zr4+ ion, BZT ceramics
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