Co2O3 substitution effects on the structure and microwave dielectric properties of low-firing (Zn0.9Mg0.1)TiO3 ceramics
Introduction
High frequency passive components such as microwave dielectric resonators and antenna have been rapidly developed for cellular phones and global positioning systems in the past decades. Low temperature co-fired ceramics (LTCC) technology has been playing a significant role in this field. Requirements for these dielectric components must combine excellent dielectric properties such as a moderate dielectric constant (εr), a low dielectric loss of the quality factor (Q × f) and a near-zero temperature coefficient of resonant frequency (τf), which allows the components to operate normally under a wide temperature range [1], [2], [3].
ZnO-TiO2 based ceramics have been one favorite research for years because of their excellent microwave dielectric properties. In their phase diagram reported by Yang and Swisher [4], three phases are known to exist: Zn2TiO4 (cubic), ZnTiO3 (hexagonal), and Zn2Ti3O8 (cubic). Zn2TiO4 can be easily prepared by the conventional solid-state reaction with mole ration of ZnO: TiO2 = 2:1, possessing microwave dielectric properties of εr = 21, Q × f = 20,000 GHz, τf = − 60 ppm/°C) [5], [6], [7]. However, its poor Q × f and τf value limits its practical application. Zn3Ti2O8 has the same cubic structure of Zn2TiO4. However, it transforms to ZnTiO3 at about 820 °C [5], [8], which has a negative impact on the properties. ZnTiO3 has a multilayer structure with excellent microwave dielectric properties (εr = 19, Q × f = 30,000 GHz, τf = − 55 ppm/°C), which decomposes into Zn2TiO4 and TiO2 when heating temperature above 945 ℃ [5], [9], [10], and it is possible for cofiring with Ag electrode (not exceed melting point of Ag, about 951 °C), which makes ZnTiO3 promising for LTCC application. Nevertheless, the Q×f value of ZnTiO3 is still not good. Our previous study shows a great enhancement in Q × f value with small amount of Mg2+ addition: εr = 20.53, Q × f = 61,630 GHz, τf = − 76 ppm/°C for (Zn0.9Mg0.1)TiO3 [11], but the τf value still too poor to be used in LTCC field.
Theoretically, since a close ionic radius of Co2+ (0.745 Å) with Zn2+ (0.74 Å) and Mg2+ (0.72 Å) at the same coordinate number [12], CoTiO3 has the same crystal structure of ZnTiO3. And in our previous work of Zn-Nb-Ti system, we found the substitution of Co2+ in Zn site has an improvement of the negative τf value and still maintain great microwave dielectric properties [13]. Thus, Co2O3 was considered to add into Zn0.9Mg0.1TiO3. And for improving its application in LTCC field, ZnO-B2O3-SiO2 (ZBS) glass was performed as a sintering aid to decrease the sintering temperature. The influence of Co2+ substitution on the crystal structure, microstructures and microwave dielectric properties of (Zn0.9Mg0.1)1−xCoxTiO3 ceramics have been investigated in detail.
Section snippets
Experimental
Samples of (Zn0.9Mg0.1)1−xCoxTiO3 (ZMCxT) were prepared with high purity materials: ZnO (Liuzhou at the Zinc Product Co., Ltd., Liuzhou, China, 99.7%), MgO (Industrial development zone, Mulan Town, Xindu, Chengdu, China, 98.0%), Co2O3 (Industrial development zone, Mulan Town, Xindu, Chengdu, China, 99.0%), TiO2 (Xiantao Zhongxing Electronic Materials Co., Ltd, Hubei, China, 99.9%). The starting materials were mixed together and then ball-milled in a nylon jar with zirconia balls for 24 h in the
Results and discussion
The X-ray diffraction patterns of ZMCxT + 3 wt% ZBS ceramics sintered at 900 °C for 4 h are displayed in Fig. 1(a). Phase compositions under different x values were indexed as ZnTiO3 phase (JCPDS # 26-1500, Hexagonal, R-3 (148)) and ZnB2O4 phase (JCPDS # 39-1126, Cubic, Im-3m (229)), no additional peaks corresponding to other phases were found. According to the phase diagram of ZnO-B2O3-SiO2, there does exist a formation of ZnB2O4 phase [15]. Rietveld refinement was applied to obtain important
Conclusion
The present work mainly discusses the influences of Co2+ substitution on the crystal structure and microwave dielectric properties of (Zn0.9Mg0.1)TiO3 ceramics. ZnTiO3 and ZnB2O4 phases coexist at x = 0.02 ~ 0.10, cell volumes decrease at 0.04 and 0.10 are mainly attributed to the bond length decrease of Zn/Mg/Co-O1(1), Zn/Mg/Co-O1(2), Ti-O1(1) and structural stability. The decrease of εr value is attributed to the decreased dielectric polarizability and the lower εr values of ZnB2O4 phase and
References (30)
- et al.
The phase stability of Zn2Ti3O8
Mater. Charact.
(1996) - et al.
Formation and transformation of ZnTiO3 prepared by sol–gel process
Mater. Lett.
(2005) - et al.
Low-temperature sintered Zn2TiO4:TiO2 with near-zero temperature coefficient of resonant frequency at microwave frequency
J. Alloy. Compd.
(2009) - et al.
ZnTiO3 ceramic sintered at low temperature with glass phase addition for LTCC applications
Mater. Chem. Phys.
(2007) - et al.
Low temperature sintering of low-loss ZnTiO3 microwave dielectric ceramics with Zn–B–Si glass
J. Alloy. Compd.
(2015) - et al.
Structure, microwave properties and low temperature sintering of Ta2O5 and Co2O3 codoped Zn0.5Ti0.5NbO4 ceramics
Mater. Chem. Phys.
(2017) Microwave dielectric properties of low loss microwave dielectric ceramics: A0.5Ti0.5NbO4 (A = Zn, Co)
J. Eur. Ceram. Soc.
(2014)- et al.
Low-temperature preparation and microwave dielectric properties of ZBS glass–Al2O3 composites
Ceram. Int.
(2009) - et al.
Effects of packing fraction and bond valence on microwave dielectric properties of A2+B6+O4 (A2+: Ca, Pb, Ba; B6+: Mo, W) ceramics
J. Eur. Ceram. Soc.
(2010) - et al.
Dielectric properties of [Ca1−x(Li1/2Nd1/2)x]1−yZnyTiO3 ceramics at microwave frequencies
Mater. Sci. Eng.: B
(2003)
Synthesis, structural, magnetic and transport properties of layered perovskite-related titanates, niobates and tantalates of the type AnBnO3n+2, A′Ak−1BkO3k+1 and AmBm−1O3m
Prog. Solid State Chem.
Low-temperature sintering and microwave dielectric properties of Ba5Nb4O15 with ZnB2O4 glass
J. Eur. Ceram. Soc.
Structure, Raman spectra, far-infrared spectra and microwave dielectric properties of temperature independent CeVO4–TiO2 composite ceramics
J. Alloy. Compd.
Low loss dielectric materials for LTCC applications: a review
Int. Mater. Rev.
High permittivity, low loss microwave dielectrics suitable for 5G resonator and low temperature co-fired ceramic architecture
J. Mater. Chem. C
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