Effects of Postdensification Annealing upon Microstructures and Microwave Dielectric Characteristics in Ba((Co_0.6−x/2Zn_0.4−x/2Mg_x)_1/3Nb_2/3)O₃ Ceramics

Abstract

Effects of postdensification annealing upon microstructures and microwave dielectric characteristics in Ba((Co 0.6Àx/2 Zn 0.4Àx/2 Mg x ) 1/3 Nb 2/3 )O 3 (x = 0, 0.1, 0.2, and 0.3) complex perovskite ceramics have been investigated. Long-time annealing at temperatures below the order-disorder transition temperature enhances the cation ordering degree and promotes the ordering domain growth. The most significant improvement of Qf value is obtained together with the suppressed temperature coefficient of resonant frequency in the samples annealed at 1400°C for 12 h, while the dielectric constant decreases slightly. The Qf value of ceramics annealed at 1400°C mainly attributes to the enhanced cation ordering degree, because their low-energy domain boundaries are not detrimental to the Qf value. As the annealing temperature increases close to the transition temperature, coarse ordering domains with high-energy boundaries are formed, and then the Qf value steadily decreases because of the inferior domain structure, even the cation ordering degree increases. The microwave dielectric characteristics of Ba((Co 0.6Àx/2 Zn 0.4Àx/2 Mg x ) 1/3 Nb 2/3 )O 3 ceramics are affected by the common function of ordering degree and domain structure. The best combination of microwave dielectric characteristics is obtained in the composition of x = 0.3 after annealing at 1400°C for 12 h: e r = 33.2, Qf = 117 200 GHz, and s f = 8.6 ppm/°C. II. Experimental ProceduresBa((Co 0.6Àx/2 Zn 0.4Àx/2 Mg x ) 1/3 Nb 2/3 )O 3 (x = 0, 0.1, 0.2, 0.3) ceramics were prepared by a routine solid-state reaction process from high-purity powders of BaCO 3 (99.93%), CoO (99.9%), ZnO (99.95%), MgO (99.9%), and Nb 2 O 5 (99.99%). The weighed starting materials were mixed by ball milling with zirconia media in ethanol for 24 h, and P. K. Davies-contributing editor Manuscript No. 33012.

Effects of MnO2 addition on quality factor of Ba(Co0.7Zn0.3)1/3Nb2/3O3 microwave dielectric ceramics

“…Therefore, The solid solutions of Ba(Co 0.7 Zn 0.3 ) 1/3 Nb 2/3 O 3 (BCZN) have been studied to obtain a zero-τ f material with high Q-value [3,4]. It is well known that the low loss of Ba(B 0 1/3 B″ 2/3 )O 3 is correlated with the 1:2 ordering in B-site cations and long-time low-temperature annealing are the most efficient way to enhance the cation ordering degree, consistent with the increase of Q Â f value [5,6]. Ahn et al [4] reported that the evaporation of CoO/ZnO existed in BCZN with the decreasing relative density.…”

Microwave dielectric properties of Ba(Co0.56Y0.04Zn0.35)1/3Nb2/3+x O3(x = −0.004 ~ 0.008) ceramics

“…They are frequently used for the production of passive microwave components like substrates for integrated circuits, mounting, dielectric filters, dielectric antennae and dielectric resonators [1][2][3][4]. Among the dra- is highlighted for its high quality factor (Q 9 f) value, adjustable temperature coefficient of resonant frequency (s f ) and low sintering temperature among this series [2,[5][6][7].…”

“…The samples with high ordering degree usually have low dielectric loss values (high Q 9 f values) [11,12]. Besides the 1:2 B-site cation ordering, there existed many literatures suggesting that the high Q 9 f characteristics were attributed to some other factors, such as impurity phases [13,14], porosity [15], lattice distortion (c/a) [16,17], grain size [18] and grain boundary [19], ordering domain structures [1,20,21], and oxygen vacancies [22]. Furthermore, the Q 9 f value of this system was considered to be very sensitive to nonstoichiometry [7,18].…”

Effects of Y2O3 substitution on microwave dielectric properties of Ba(Co0.6Zn0.38)1/3Nb2/3O3 ceramics

“…The result reveals that the intensity of (100) peak exhibiting an increase in the initial region (x = 0-0.02), but when the doping content exceeding x = 0.02, it decreases with increasing dopant amount. It has been reported that the evolution of ordering degree can be evaluated using a parameter (S) calculated by comparing the (100) (2h = 17.6°) superlattice reflection intensities with that of the strongest peak (110,102) from the below XRD patterns [30,31]: The ratio of the integral intensity of superlattice peak to the strongest peak in theory is calculated through placing all the atoms in ideal positions of the ordered hexagonal lattice. The S value with different x are shown in Fig.…”