Elsevier

Journal of Alloys and Compounds

Volume 655, 15 January 2016, Pages 60-65
Journal of Alloys and Compounds

Characterization and microwave dielectric properties of wolframite-type MgZrNb2O8 ceramics

https://doi.org/10.1016/j.jallcom.2015.09.143Get rights and content

Highlights

  • New MgZrNb2O8 ceramics were prepared by the solid-state and sol–gel method.

  • The sample was sintered at 1225 °C with εr = 27.08, Q·f = 29,070 GHz by solid-state reaction.

  • The sample was sintered at 1175 °C with εr = 22.16, Q·f = 29,490 GHz by sol–gel process.

Abstract

Wolframite type MgZrNb2O8 ceramics were prepared by solid-state method and sol–gel process in this study, and the influence of sol–gel process on the sintering behavior and microwave dielectric properties of MgZrNb2O8 ceramics was investigated. The optimal sintering temperatures of MgZrNb2O8 ceramic for solid-state and sol–gel method were 1225 °C and 1175 °C, respectively. For solid-state method, MZN ceramics sintered at 1225 °C with nearly full density had the microwave dielectric properties of εr = 27.08, Q·f = 29,070 GHz and τf = −24.31 ppm/°C. For sol–gel process, MZN ceramics sintered at 1175 °C with nearly full density had excellent microwave dielectric properties of εr = 22.16, Q·f = 29,490 GHz and τf = −15.99 ppm/°C. Obviously, sol–gel synthetic route could significantly reduce the sintering temperature and improve the microwave dielectric properties.

Introduction

In recent decades, microwave dielectric ceramics developed rapidly, and have been the basis for the realization of microwave control function and the key materials to the microwave devices (such as resonator, phase shifter, etc.) widely used in modern communication [1], [2], [3], [4]. In order to meet the demand for miniaturization and integration, it is increasingly needed to expand the search for new microwave dielectric materials, which should have appropriate dielectric constant (εr), high quality factor (Q·f), near-zero temperature coefficient of resonant frequency (τf) [5]. At present, many types of compounds were reported for the possible use in microwave applications [6], [7], [8], [9], [10]. Among several kinds of microwave dielectric ceramics with low dielectric constant, wolframite-type MgZrNb2O8 (MZN) ceramics possess excellent properties, high quality factors combined with appropriate dielectric constant.

MZN ceramics were always prepared by the conventional solid-state method in the past reports [11], [12]. For instance, Y. Cheng et al. [11] reported that MZN ceramic was obtained at 1340 °C for 4 h by the solid-state method with εr = 26, Q·f = 120,816 GHz and τf = −50.2 ppm/°C. In addition, S.D. Ramarao and V.R.K. Murthy [12] also reported that the MZN ceramics could be sintered at 1500 °C via the traditional solid-state method and exhibited the microwave dielectric properties: εr = 9.60, Q·f = 58,500 GHz and τf = −31.5 ppm/°C. As reported in the past, the major disadvantage of solid-state method was higher sintering temperature. Sol–gel process not only had advantages of high purity and homogeneous grain size, but also lowered the sintering temperature as well as improved the dielectric properties. However, little research regarding preparation of MZN ceramics by the aqueous sol–gel process has been reported in the literature to date. In the following study, a wolframite MZN ceramic was prepared by solid-state method and sol–gel process. The effects of sol–gel process on sintering temperature, phase compositions, microstructures and microwave dielectric properties of MZN ceramics were also investigated in detail.

Section snippets

Experimental procedure

High-purity oxide MgO (99%), ZrO2 (99.99%) and Nb2O5 (99.9%) were used as raw materials to synthesize the MZN powders by the solid state method. The raw materials were weighed and mixed according to the formula of MgZrNb2O8. The mixed powders were ball-milled for 8 h with distilled water in a nylon container with ZrO2 balls. All the slurries were dried and pre-sintered at 1050 °C for 4 h to obtain single phase MZN. Then the powders were re-milled for 6 h. Analytical-grade Mg(NO3)2·6H2O, Zr(NO3)4

Results and discussion

The X-ray diffraction patterns of MZN powders calcined at 900°C–1100 °C for 2 h are illustrated in Fig. 1(a). As shown in Fig. 1(a), ZrO2 (JCPDS No. 83-0938) as secondary phase was observed at 900 °C, and the peak intensity of it decreased with the calcining temperature increasing. It is obvious that powders were not reacted completely at lower temperature. There was no significant change in the X-ray diffraction patterns of MZN powders with the calcining temperature increasing from 1000 °C to

Conclusions

MgZrNb2O8 ceramics with wolframite type were prepared by solid-state method and sol–gel process in this study, and the influence of sol–gel process on sintering temperature, phase compositions, microstructures and microwave dielectric properties of MZN ceramics were also investigated. For solid-state method, MZN ceramics with nearly full densities were obtained at 1225 °C with microwave dielectric properties of εr = 27.08, Q·f = 29,070 GHz and τf = −24.31 ppm/°C. And for sol–gel process, MZN

Acknowledgments

This work was supported by the Project development plan of science and technology of ji'nan city (No.201303061), Ji'nan City Youth Science and Technology Star Project (No.2013035), and National Natural Science Foundation (No. 51472108) and Study Abroad Programs by Shandong Province Government.

References (22)

  • D. Cruickshank

    J. Eur. Ceram. Soc.

    (2003)
  • W. Wang et al.

    J. Alloys Compd.

    (2015)
  • M. He et al.

    J. Alloys Compd.

    (2014)
  • C. Liu et al.

    J. Alloys Compd.

    (2015)
  • R. Muhammad et al.

    J. Alloys Compd.

    (2015)
  • M.A. Nath et al.

    J. Alloys Compd.

    (2014)
  • S.D. Ramarao et al.

    Scr. Mater.

    (2013)
  • Y. Cheng et al.

    Ceram. Int.

    (2013)
  • C.L. Huang et al.

    Mater. Res. Bull.

    (2000)
  • H. Tamura

    J. Eur. Ceram. Soc.

    (2006)
  • A. Terrell Vanderah

    Science

    (2002)
  • Cited by (26)

    • Correlation between crystal structure and enhanced microwave dielectric characteristics of wolframite-structure Mg<inf>0.5</inf>Zr<inf>0.5</inf>NbO<inf>4</inf> ceramics

      2022, Ceramics International
      Citation Excerpt :

      For instance, Wu et al. synthesized Mg0.5Zr0.5NbO4 ceramics through an effective and simple reaction-sintering procedure with high Q × f value [10]. Wu et al. adopted sol–gel process to synthesize Mg0.5Zr0.5NbO4 ceramics and obtained satisfactory dielectric performance: εr = 22.16, Q × f = 29,490 GHz, τf = −15.99 ppm/°C at 1175 °C [11]. Additionally, ionic substitutions are a valid tool for performance modification.

    View all citing articles on Scopus
    View full text