Microstructural and electrical properties of multicomponent varistor ceramics with PbO–ZnO–B2O3 glass addition

Abstract

Zinc oxide based ceramics are widely used materials in varistors because of their excellent nonlinearity. Traditionally these ceramics are sintered at high temperatures (about 1,100-1,300°C). In this work a novel zinc oxide-based material with a low sintering temperature (900-1,000°C) was investigated. This material can be used in varistors consisting of several ceramic layers with embedded silver/palladium thick-film electrodes. This paper explains the research procedure employed with this novel varistor material, including the effect of sintering aid addition on the final electrical properties and fired microstructure. The electrical properties achieved are compared to the values measured from the original zinc oxide composition without sintering aid addition. Especially the I-V characteristics, nonlinearity coefficient !, breakdown voltage V bk and leakage current density J L are investigated. The sintering properties are also reported. It was found that by adding 10 wt.% of glass and using a 900°C sintering temperature, the material had good varistor characteristics, as V bk =378 V/mm, !=33 and J L =15 μA/cm 2 . The investigated varistor material can be applied to protect electrical circuits against surges.

Spectroscopic properties and ab initio calculations on the structure of erbium–zinc-borate glasses and glass ceramics

“…The erbium ions are situated between the layers. Moreover, the application of high pressure or high temperature can cause layers rebuilding from the non-cyclic 4 ] tetrahedral units (900-1100 cm − 1 ) [12][13][14][15]. The antisymmetric stretching mode causes that bands are centered at about 1050 cm − 1 , whereas the symmetric stretching frequency is located in the 850-900 cm − 1 region.…”

“…The Zn-O distances in the [Zn 4 O] polyhedra are divided into two sets: a set of three shorter distances ranging from 1.83 to 1.91 Å and one with a longer interatomic distances (4.27 Å) than the sum of the van de Waals radii. Accordingly, the formation of three-coordination oxygens was necessary to compensate shortage of oxygens from zinc atoms.…”

“…The Zn + 2 ions occupy in the glass-ceramic network both forming and modifying positions [3]. Then, zinc oxide-based ceramics are widely used materials in varistors because of their excellent nonlinearity [4].…”

Low‐temperature sintering and electrical properties of BBSZ glass‐doped ZnO‐based multilayer varistors

“…Sintering with low‐melting point glass is the most effective and economical method for realizing high density of sintered ceramics at relatively low sintering temperatures . It has reported that the fabrication of MLVs with glass additives can evidently lower the sintering temperature, but at the same time, it will have some side effects on its nonlinear coefficient and voltage gradient as excessive dopant added . Consequently, there is a need to develop low‐temperature sintering MLVs with good nonlinear characteristics.…”

LOW-TEMPERATURE SINTERING OF ZnO-Bi₂O₃-BASED VARISTOR CERAMICS FOR ENHANCED MICROSTRUCTURE DEVELOPMENT AND CURRENT-VOLTAGE CHARACTERISTICS

“…Temperatures below 1000°C would also enable the use of cheaper Ag contacts instead of the much more expensive Pd-or Ptcontaining ones [9][10][11][12][13][14][15]. Different approaches have been reported in order to prepare dense varistor ceramics with good I-U characteristics at temperatures below 1000°C, such as the use of fine starting powders with a high sinterability prepared by a polymerized complex method [16], a two-stage, low-temperature thermal processing [17,18], hot pressing [19] or the addition of low-melting glass frit [10,20]. They resulted in a high density of varistor ceramics; however, the breakdown voltages of the ceramics were still above 1000 V·mm -1 , which is much too high for most applications.…”