Varistors are the ceramic elements which are designed to protect electrical devices against overvoltage hazard. Their ability to handle the overvoltages results from the particularities of their V=R(I) characteristics i.e when exposed to high voltage transients the varistor impedance decrease many orders of magnitude, thus clamping the transient voltage to a safe level.

The ZnO varistors are processed by mixing the ZnO with a small amount of other metal oxides and although every metal oxide additive has its role to fulfill, the Bi₂O₃ is crucial for inducing the non-linear property into ZnO ceramic. The non-ohmic behavior is brought about during varistor sintering when a number of processes and reactions is taking place in this system.
The basing process occurring during varistor sintering is the high-temperature (1050^oC)     Bi₂(Zn_4/3Sb_2/3)O₆ pyrochlore phase reaction with ZnO. In the result forms alfa-Zn₇Sb₂O₁₂ spinel and Bi₂O₃, which is in liquid phase at this temperature. The Bi₂O₃ along with dopands dissolved in it penetrates into the intergrain regions and, by modifying them, influences varistor electrical properties. Varistor electrical properties depend also on the size of ZnO grains. The alfa-Zn₇Sb₂O₁₂ spinel hinders the grain growth during sintering. In this work the varistor ceramics was added with BaBiO_3-x. The BaBiO_3-x was to act as a substitute of pyrochlore phase. As BaBiO_3-x does not react with ZnO, as its reagent the TiO₂ was applied. The crystal phases measurements were performed with DRON 2 difractometer using Fe filtered Co radiation. The mixture of BaBiO_3-x  and TiO₂ were placed on Pt plate. As it appeared, due to the action of temperature, in the investigated (BaBiO_3-x + TiO₂) sample the TiO₂ reflexes disappear at temperature about 700^oC but quality changes of BaBiO_3-x phase are observed at higher temperatures by appearance of ß Bi₂O₃ crystal phase, what proves that BaBiO_3-x and TiO₂ went into reaction, although the (Ba,Ti) product of this reaction must be in subcrystalline form.

The ß  Bi₂O₃ appearance give the evidence that the BaBiO_3-x phase can be successfully applied in varistor technology.

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