Ba(Zn_1/3Ta_2/3)O₃ Ceramics for Microwave and Millimeter‐wave Applications

Abstract

The Ba(Zn(1/3)Ta(2/3))O(3) (BZT) ceramic samples were prepared by solid-state reaction and sintered in the range 1550-1650 degrees C for 2 h. Several methods--X-ray diffraction (XRD) and scanning electron microscopy (SEM)--were used for structural and morphological characterization. The unit cell distortion and the presence of the secondary phase content were studied by XRD. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was noticed with the increase of the sintering temperature. SEM investigations revealed polyhedral well-faceted grains and large grain size distribution. The dielectric properties in the microwave range were measured at room temperature and at 1 kHz on a large temperature interval (+/-150 degrees C). The dielectric parameters were correlated with morphological and structural properties. Ceramic samples were annealed at 1410 degrees C for 30 h to improve the microwave properties. The dielectric constant of BZT samples measured at 6 GHz and at 1 kHz was between 27 and 28 on the whole temperature range, that is, typical values for BZT material. The temperature coefficient of the resonance frequency at 6 GHz exhibits positive values less than 6 ppm/degrees C.

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

“…The very high Q × f values up to 120 THz were achieved in this paper for a 99.95% purity Ta 2 O 5 raw material and for a sintering time increased from 2 h [18,19] to 4 h. The 120 THz achieved in this work for Q × f is in the same range of previously reported values, which were obtained at longer sintering times and with supplementary annealing treatments [4].…”

“…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).…”

“…As a result of our previous investigations, high-Q BZT dielectric resonators (Q ∼ 17,000 at 5.6 GHz) were achieved by solid-state reaction [18,19]. The aim of this work is a further increase of the quality factor.…”

A low-loss dielectric using CaTiO₃-modified Mg_1.8Ti_1.1O₄ ceramics for applications in dielectric resonator antenna

“…In addition, a low-dielectric-loss for better selectivity and a near-zero temperature coefficient of resonant frequency (τ f ) for stable frequency stability is also critical requirements for practical applications. Demand for developing new low-cost, low permittivity materials with a high Qf has become more important than ever due to the carrier frequency of interest in communication systems was extended from GSM900 MHz to ISM bands (2.4,5.2,and 5.8 GHz) or even to the millimeter wave range [12]. Consequently, the search for low-loss dielectric ceramics has become a primary issue in the last few years [12][13][14][15][16].…”