Preparation of Strontium Titanate Ceramics and Internal Boundary Layer Capacitors by the Pechini Method
- PDF / 1,326,321 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 13 Downloads / 196 Views
PREPARATION OF STRONTIUM TITANATE CERAMICS AND INTERNAL BOUNDARY LAYER CAPACITORS BY THE PECHINI METHOD
K. D. BUDD AND D. A. PAYNE Department of Ceramic Engineering and Materials Research Laboratory University of Illinois at Urbana-Champaign 105 South Goodwin Avenue, Urbana IL 61801
ABSTRACT High purity, fine-grain size, SrTi0 3 ceramics were fabricated from powders which were chemically derived by the Pechini method. The preparation is based upon a thermally polymerizable water-ethylene glycol-citric acid system in which a wide range of metal alkoxides, carbonates, and metal salts are soluble. The process is a closed system, and lends itself to the preparation of complex oxides which can contain numerous additives and dopants. In this study, Wdoped SrTiO3 powders were prepared with various Sr:Ti ratios, and fine grain internal boundary layer capacitors were fabricated by controlled segregation in sintering. Characteristics of the resin, powder, microstructures, and electrical properties are reported. The advantages and disadvantages of this method of chemical preparation for ceramic materials are noted.
INTRODUCTION Strontium titanate is
one of a large number of titanate perovskite
materials which are widely used
in
the electronic
ceramics
industry.
The
widespread use of titanates is a result of their highly polarizable crystal structure, and of the wide range of electrical properties possible through chemical modifications and process control manipulations. The latter is exploited in internal boundary layer capacitors, base metal electrode compatible dielectrics, and highly conducting ceramic electrodes. It is in these newer applications that the degree of process control afforded by conventional ceramic processing methods has often been inadequate. As a result, the use of novel methods of chemical preparation has increased dramatically over the past few years, as in other areas of high technology ceramics. In this study, a liquid solution resin-forming technique, known as the Pechini method [11, was used to prepare high purity W-doped SrTiO3 powders. This method can be used to produce a variety of oxide materials including titanates, zirconates and niobates. As described in the orignial patent [11, polybasic acid chelates are formed from alpha hydroxycarboxylic acids, such as citric acid, with titanium, zirconium, or niobium containing solutions. When heated with a polyhydroxy alcohol, such as ethylene glycol, polyesterification and resin formation gradually occurs. Details of the procedure are given later. Since a variety of different chemical methods of ceramic powder preparation are now available,
it
is
useful
to note the fundamental
differences between, and compare the advantages and disadvantages of, specific method with its various alternatives.
Mat.
Res. Soc. Syop.Proc. Vol. 32 (1984)
Published by Elsevier Science Publishing Co.,
Inc.
a
240
COMPARISON OF CHEMICAL METHODS Nearly all chemical powder preparation techniques offer the potential for finer uniform particle size distributi
Data Loading...
