Effects of Mg Substitution on Order/disorder Transition, Microstructure, and Microwave Dielectric Characteristics of Ba((Co_0.6Zn_0.4)_1/3Nb_2/3)O₃ Complex Perovskite Ceramics

Abstract

Effects of Mg substitution on order/disorder transition, microstructure, and microwave dielectric characteristics of Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics have been investigated. The ordered complex perovskite solid solutions are obtained in Ba((Co0.6−x/2Zn0.4−x/2Mgx)1/3Nb2/3)O3 ceramics (x = 0, 0.1, 0.2, and 0.3), and the ordering degree in the as‐sintered dense ceramics increases with increasing Mg‐substitution amount. The significantly improved Qf value is obtained in the present ceramics with increasing x, whereas the dielectric constant decreases slightly together with some increase of temperature coefficient of resonant frequency. The best combination of microwave dielectric characteristics is obtained in the composition of x = 0.3: εr = 33.7, Qf = 93 800 GHz, and τf = 9.6 ppm/°C. In the Mg‐substituted compositions, clear domain boundaries are obtained and the domain size increases as x increases, the highest Qf value is obtained when the domain size is about 40–60 nm in the ceramics with x = 0.3. The increased ordering degree and the fine ordering domain structure are considered to primarily contribute to the significant increase of Qf value in the Mg‐substituted Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics.

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

“…Figure 6 illustrates the s f value of the Ba(Co 0.6-x Y x Zn 0.38 ) 1/3 Nb 2/3 O 3 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.06) ceramics sintered at 1375°C for 20 h. For a composite ceramic, the s f value primarily depends on its phase composition. In previous studies [4,22], the changes of the s f value presented an increasing tendency as a function of the addition amount for BCZN ceramics, which can be attributed to relatively higher s f value of the secondary phase. The s f values in our work also increased with increasing doping content.…”

“…5, it is found that there was much relation between the Q 9 f values and the microstructure. Although it is believed that the microwave dielectric loss of the BCZN ceramics is mainly affected by the 1:2 ordered hexagonal structure, the impurity phase, the porosity, and grain size also influence the microwave dielectric loss [4]. The composition exhibiting the optimum microstructure in the field of, e.g., high c/a ratio, pure phase, uniform grain size distribution, few pores composition can usually possess a high Q 9 f value.…”

“…; B 00 = Ta, Nb) complex perovskite ceramics,which possess suitable microwave dielectric properties, have been extensively researched. Among them, Ba(Zn 1/3 Nb 2/3 )O 3 -Ba(Co 1/3 Nb 2/3 )O 3 (BZN-BCN, BCZN) with high quality factor (Q 9 f) value, adjustable temperature coefficient of resonant frequency (s f ), comparatively cheap price of Nb 2 O 5 , and low sintering temperature is highlighted [1,[4][5][6]. The microwave dielectric properties of BZN is e r = 41.0, s f = 30 ppm/°C [7], whereas that of BCN is e r = 32.0, s f = -12 ppm/°C [8], suggesting that the e r and s f can be varied by changing the composition.Then it is well recognized that the high Q 9 f achieved in these complex perovskites is mainly connected with the 1:2 ordered hexagonal structure [3,4,9,10].…”

“…The low loss values are obtained when the samples exhibit high ordered degree [3,11]. Besides the 1:2 B-site cation ordering, the high Q 9 f characteristic can also be attributed to some other factors, such as ordering domain structures [4,12,13], lattice distortion (c/a) [14,15], impurity phases [16,17], grain size [18] and grain boundary [19], porosity [20], and oxygen vacancies [21].…”

“…In order to obtain relative high Q 9 f and adjust s f to zero, BCN and BZN have been modified using various valence states of different oxides, such as Al 2 O 3 [22], MgO [4,23], SnO 2 [24], SrO [25], WO 3 [24,26], ZrO 2 [1], Ta 2 O 5 [3], etc. Wu et al [26].…”