制备Ba(Mg1/3Nb2/3)O3纳米粉末的新溶胶-凝胶法

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"A new sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 nanopowders (2004年)"是工程技术领域的一篇论文，发表在《北京科技大学学报》2004年第11卷第1期第48页。该研究由 Fang Lian、Lihua Xu、Fushen Li 和 Hailei Zhao 于2003年4月16日完成。文章主要探讨了一种新型的溶胶-凝胶法制备Ba(Mg1/3Nb2/3)O3纳米粉末的方法。在论文中，研究人员使用市售的五氧化二铌（Nb2O5）作为基础材料，与醋酸钡[Ba(CH3COO)2]和醋酸镁[Mg(CH3COO)2·4H2O]共同参与溶胶-凝胶过程。首先， Nb2O5与熔融的氢氧化钠反应，转化为可分散的氧化物。经过冷却后，得到的玻璃状物质被分散并用蒸馏水多次洗涤，以去除其中的钠离子。制备好的 Nb2O5·nH2O 非均相溶液随后与醋酸钡和醋酸镁按所需摩尔比例混合，接着进行凝胶化。最终，通过在820℃下对凝胶进行热处理，得到了超细的Ba(Mg1/3Nb2/3)O3粉末。 Ba(Mg1/3Nb2/3)O3，简称BMN，是一种多铁性材料，具有优异的介电性能和压电特性，常用于电子陶瓷和多功能复合材料。溶胶-凝胶法是一种常见的纳米材料制备技术，其优点在于可以控制粉末的粒径大小，提高材料的均匀性和纯度，且工艺相对简单。在本研究中，通过调整化学反应条件，如反应物的比例、pH值、热处理温度和时间等，可以优化Ba(Mg1/3Nb2/3)O3纳米粉末的物理和化学性质。例如，热处理温度对于形成结晶度高的粉末至关重要，而控制Na+离子的去除则有助于提高粉末的纯度和稳定性。此外，溶胶-凝胶法制备的纳米粉末具有良好的分散性和颗粒尺寸分布，这在实际应用中非常重要，因为它们直接影响材料的性能和加工性能。因此，这项工作不仅揭示了Ba(Mg1/3Nb2/3)O3纳米粉末的制备方法，也为优化多铁性材料的性能提供了新的思路和技术支持。

Journal of University of Science and Technology Beijing

Volume 11, Number 1, February 2004, Page 48

Corresponding author: Fang Lian, E-mail: lianfang2000@263.net

Materials

A new sol-gel process for preparing Ba(Mg

1/3

2/3

nanopowders

Fang Lian, Lihua Xu, Fushen Li, and Hailei Zhao

Department of Inorganic Materials, University of Science and Technology Beijing, Beijing 100083, China

(Received 2003-04-16)

Abstract: Commercially available niobium (V) oxide [Nb

], with barium acetate [Ba(CH

COO)

] and magnesium acetate

[Mg(CH

COO)

4H

O] was used as the starting material in the sol-gel process for preparing Ba(Mg

1/3

2/3

(BMN) nanopowders.

At first, Nb

reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassy substance after

cooling was dispersed and washed several times in distilled water to remove the Na

ions. The as-prepared colloidal Nb

nH

was subsequently mixed with acetic solution of barium acetate and magnesium acetate according to the required molar proportions

and followed by gelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820C for 1 h, and the

as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwave Q-factor, of 10397 at 1.45GHz.

Key words: Nb

nH

O colloid; Ba(Mg

1/3

2/3

nanopowder; sol-gel processing; microwave Q-factor

1 Introduction

With the development of advanced communication

systems, there is an ever-increasing demand for cheap

but high performance microwave dielectrics. The ef-

fective dielectric materials should have a sufficiently

high relative permittivity, low dielectric losses and a

temperature coefficient of resonant frequency near

zero [1]. The complex perovskite Ba(Mg

1/3

2/3

(BMN) [2] and Ba(Mg

1/3

2/3

(BMT) [3-5] are

currently available dielectric ceramics. It is known

that tantalum is a much more expensive metal, the ore

tantalite (60% Ta

) costing $150 per kg, but nio-

ium is over 20 times cheaper [6]. So the BMN would

be one of candidate materials of relative cheap and

high performance dielectric ceramics.

As reported, the preparation routes of BMN powd-

ers are primarily based on the solid-state reaction me-

thod [7-8], in which high temperature is often required

to promote the ion diffusion among various oxides.

And the so obtained BMN powders are usually coarse

and agglomerated, which are harmful to the properties

of the final ceramics.

Wet-chemical processes have been widely regarded

as an efficient route to synthesize homogeneous na-

no-crystalline particles at low temperatures. Some

works have been reported to synthesize the BMN

powders via a necessary precursor, niobium alkoxide

derived from the expensive starting powders NbCl

However, the process for preparing niobium alkoxide

would take a so long time and need the protected at-

mosphere [9,10]. Furthermore, the NbCl

was more

difficult to be prepared experimentally because of its

unstable chemical characteristics. This paper presents

a simple and novel approach to prepare BMN nano-

powders with high sinterability. Nb

, due to its

lower cost and abundant resource, was selected as the

starting material to prepare a high quality colloidal



O, instead of the currently used

Nb(OC

)

precursor. The fine BMN powders could

be finally obtained after mixing the as prepared col-

loidal Nb

nH

O with Mg-acetate and Ba-acetate

and followed gelation and heat treatment. The micro-

structure and the infrared absorption spectra of the

synthesized powders were characterized and examined.

In addition, the microwave dielectric properties were

reported.

2 Experimental procedure

2.1 Preparation of BMN powders and ceramic

is a kind of almost insoluble substance, ex-

cept in alkali bisulfate, alkali carbonate or caustic al-

kali. It must be transformed into dispersible oxide so

as to improve the activity of Nb

to be used as a key

precursor. In the present work, caustic soda was cho-

sen as a fluxing agent to melt Nb

. These mixture

powders of Nb

and NaOH were put in corundum

crucible and vigorously stirred while heating to

200-300C on a hot plate for about 15 min. The mol-

ten mixture was then moved into a muffle furnace and

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