Preparation, microstructure and microwave dielectric properties of ZrxTi1−xO4 (x=0.40–0.60) ceramics

doi:10.1016/S0955-2219(01)00226-6

Journal of the European Ceramic Society

Volume 21, Issue 16, December 2001, Pages 2931-2936

https://doi.org/10.1016/S0955-2219(01)00226-6 Get rights and content

Abstract

Zr_xTi_1−xO₄ (x=0.40–0.60) ceramics sintered without additives were prepared from powders made by the coprecipitation of metal salts from aqueous solutions in order to investigate the existence range of a homogeneous phase and the relationships between composition, microstructure and the dielectric properties. XRD, TEM, SEM, EDS, and the dielectric measurements were used to characterize the products. A homogeneous solid solution was obtained. Its crystal structure was isomorphous with ZrTiO₄. The variation of the lattice parameters with TiO₂ content was discussed. The optimum sintering temperature of samples was dependent of composition. TiO₂ suppressed the densification and acted as a grain growth enhancer during the sintering process. With the increase in TiO₂ content the relative densities of the sintered bodies decrease, while the grain sizes increase. The dielectric properties at microwave frequency (1.8 GHz) in this system, especially Q value, were poor, due to low densification, impurities and lattice defects. The dielectric constant ε_r and Q value exhibited a significant dependence on the relative density and composition. Both ε_r and Q increased with the increase in relative density, but they were primarily influenced by the composition and the effect of the relative density could be ignored when the relative density was greater than 90% theoretical. ε_r increased slightly with increasing TiO₂ content, while Q value decreased.

Introduction

Communication at microwave frequencies has been required with advances in communication networks. Many kinds of dielectric materials have been investigated for microwave applications.1, 2, 3, 4 Among them, zirconium titanate (ZrTiO₄)-based ceramics, which have a high dielectric constant, a high Q value and a low temperature coefficient of resonant frequency, are received special attention.5, 6, 7 Many papers focused on improving the microwave dielectric properties of ZrTiO₄-based ceramics with various kinds of additives.8, 9, 10, 11, 12, 13

ZrTiO₄ can be prepared by solid state reaction between ZrO₂ and TiO₂ at elevated temperature (1200–1600°C) and long heating times.¹⁴ For these reasons various chemical methods have been developed in order to produce reactive precursors to yield ZrTiO₄ powders by thermal treatment at lower temperature.15, 16, 17, 18 ZrTiO₄-based ceramics are often processed with sintering additives. It is difficult to fully density ZrTiO₄ without sintering additives. Sintering aids used for ZrTiO₄-based ceramics are added as a combination of two or more oxides from ZnO, CuO, NiO, La₂O₃ etc.7, 8, 9, 10, 11, 12, 13 These additives, however, lead to the degradation of its dielectric properties, due to the formation of second phase at grain boundaries. Therefore, reduction of the amounts of additives has been required for improvement of the dielectric properties. The chemical preparation of reactive precursors, especially by the coprecipitation route which utilizes solution chemistry, offers advantages over traditional processing techniques because of the fined grained powders, better homogeneity obtained and the lower processing temperature. The densification and the dielectric properties of ZrTiO₄-based ceramics may be improved if the samples are prepared from powders made by the coprecipitation method and sintered without additives. But, until now it seems not to be concerned in the other literatures.

In this paper results are presented for the production and the microwave dielectric properties of ZrTiO₄ solid solutions, Zr_xTi_1−xO₄ (x=0.40–0.60) ceramics, which are prepared from powders made by the coprecipitation of metal salts from aqueous solutions and sintered without additives. Our study is concerned with the dielectric properties of samples made by the chemical method and the relation of some physical properties of ZrTiO₄ solid solutions, Zr_xTi_1−xO₄ (x=0.40–0.60) to the composition. Five compositions are selected to span the ZrTiO₄ solid solution range based on the ZrO₂–TiO₂ phase diagram.¹⁹

Section snippets

Materials and preparation

Zr_xTi_1−xO₄ (x=0.40, 0.45, 0.50, 0.55, 0.60) powders were synthesized as follows. A 0.5 mol/l aqueous solution of zirconium oxychloride and titanium sulfate in the requisite Zr/Ti molar ratio of the desired product was dropped into extensive dilute ammonia solution with pH maintained at 9±0.1 under stirring to produce coprecipitate of Zr–Ti hydroxides. The precipitates were filtered, washed with deionized water to remove the anions taken into the precipitates by the starting materials. Next, the

Formation and crystal structure

All starting powders are amorphous. Thermogravimetric examination shows weight losses of ∼20% at 170°C in all starting powders. These can be attributed to the release of absorbed and hydrated water. Differential thermal analysis curves for all starting powders show sharp exothermic peaks. The peaks are found to result from the crystallization of ZrTiO₄ phase. The data in Table 1 show that the temperature of crystallization is shifted to higher temperatures from A to C, but then to lower

Conclusions

1.
ZrTiO₄ solid solutions, Zr_xTi_1−xO₄ (x=0.40–0.60) prepared by the coprecipitation of zirconium and titanium metal salts crystallize at low temperature from amorphous materials between 40 and 60 mol% TiO₂. As zirconium is substituted for titanium, the solid solutions can be indexed in an orthorhombic unit cell with a and c decreasing from 0.4841 to 0.4780 nm and from 0.5049 to 0.5017 nm, respectively, and b increasing from 0.5411 to 0.5457 nm. The volume of the unit cell decreases continuously

Acknowledgements

This work is supported by the National Natural Science Foundation of China (under Grant No. 5950062) and the National Outstanding Young Scientists Foundation of China (under Grant No. 59425007). This work is also supported by the Opening Foundation of Tsinghua Laboratory.

References (27)

D Houivet et al.
Phases in La₂O₃ and NiO doped (Zr,Sn)TiO₄ microwave dielectric ceramics
J. Eur. Ceram. Soc.
(1999)
A Bianco et al.
Zirconium titanate microwave dielectrics prepared via polymeric precursor route
J. Eur. Ceram. Soc.
(1999)
T Sato et al.
Improvement of thermal stability of yttria-doped tetragonal polycrystals by alloying with various oxides
Int. J. High Tech. Ceram.
(1986)
Y.C Heiao et al.
Microwave dielectric properties of (Zr,Sn)TiO₄ ceramic
Mater. Res. Bull.
(1988)
H.M O'Bryan et al.
A new BaO–TiO₂ compound with temperature-stable high permittivity and low microwave loss
J. Am. Ceram. Soc.
(1974)
S Nomura et al.
Ba(Mg_1/3Ta_2/3)O₃ ceramics with temperature-stable high dielectric constant and low microwave loss
Jpn. J. Appl. Phys.
(1982)
S Kawashima et al.
Ba(Zn_1/3Ta_2/3)O₃ ceramics with low dielectric loss at microwave frequencies
J. Am. Ceram. Soc.
(1983)
K Wakino et al.
Microwave characteristics of (Zr,Sn)TiO₄ and BaO–PbO–Nd₂O₃–TiO₂ dielectric resonators
J. Am. Ceram. Soc.
(1984)
Campbell, S.S., Temperature stable dielectric composition at high and low frequencies. US Pat. 4785375, 15 November...
A.J Moulson et al.
Electroceramics
(1990,)

F Azough et al.

The relationship between the microstructure and microwave dielectric properties of zirconium titanate ceramics

J. Mater. Sci.

(1996)

D.M Iddles et al.

Relationships between dopants, microstructure and the microwave dielectric properties of ZrO₂–TiO₂–SnO₂ ceramics

J. Mater. Sci.

(1992)

K.H Yoon et al.

Microwave dielectric properties of (Zr_0.8Sn_0.2)TiO₄ ceramics with pentavalent additives

J. Mater. Res.

(1995)

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High-energy ball-milling of monoclinic (m) ZrO₂–anatase (a)TiO₂ mixture (3:2 molar ratio) at room temperature results in partial formation of nanocrystalline orthorhombic ZrTiO₄ phase after 8 h of milling. ZrTiO₄ phase is formed from the high pressure srilankite (s)-TiO₂ based TiO₂–ZrO₂ solid-solution. In-situ high temperature annealing of ZrTiO₄, m-ZrO₂ and a-TiO₂ powder mixture results in complete transformation of ZrTiO₄ at 1073 K. Microstructure characterization of the ball-milled and in-situ annealed samples in terms of several lattice imperfections is made employing the Rietveld’s method of structure refinement using X-ray powder diffraction data. Phase transformation kinetics and in addition to microstructure parameters, relative phase abundances of different phases are revealed from the Rietveld analysis. The analysis reveals that the ZrTiO₄ is formed from the isostructure s-TiO₂ based TiO₂–ZrO₂ solid-solution with ∼11 nm particle size after annealing at 1073 K.

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Preparation, microstructure and microwave dielectric properties of ZrxTi1−xO4 (x=0.40–0.60) ceramics

Abstract

Introduction

Section snippets

Materials and preparation

Formation and crystal structure

Conclusions

Acknowledgements

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