Low-temperature sintering of high potential gradient B2O3-doped ZnO varistors

Abstract

High voltage gradient ZnO-Bi 2 O 3 -based varistor ceramics doped with different amounts of B 2 O 3 were prepared by the conventional ceramics processing at low temperature and their phase transformation, microstructure and electrical properties were investigated. B 2 O 3 addition promoted the formation of a liquid phase along the grain boundary and triple junctions of the ZnO grains and improved electrical properties. ZnO-Bi 2 O 3 -based varistors with nonlinearity coefficients (a) exceeding 45, the leakage current (I L ) not more than 0.1 lA and breakdown fields ranging from 880 to 1450 V/mm were obtained by doping with 0.5-2 wt% B 2 O 3 at the sintering temperature of 850°C and dwelling time of 5 h.

Sol–gel synthesis of doped nanocrystalline ZnO powders using xanthan gum and varistor properties study

“…ZnO varistors doped with only a small amount of oxides of Bi, Co, Cr, Mn and others possess exceptional nonlinearity in their voltage (E)-current (J) characteristics and the ability to absorb large amounts of energy [6]. For this reason, ZnO varistors are the most widely used in several applications from small current electronic circuits to large current transmission lines because of their highly nonlinear current-voltage characteristics and energy handling capabilities [7].…”

“…The homogeneous starting powder is necessary for the manufacture of high performance ZnO varistors [7,8]. It is difficult for the conventional oxide mixing route to obtain homogeneous composite powder [7,9], so several chemical methods have been developed in the past including sol-gel technique [10], microemulsion synthesis [11], coprecipitation [12] and polymerized complex method [13].…”

“…It is difficult for the conventional oxide mixing route to obtain homogeneous composite powder [7,9], so several chemical methods have been developed in the past including sol-gel technique [10], microemulsion synthesis [11], coprecipitation [12] and polymerized complex method [13]. For solgel method, it has attracted much attention because of its relatively low processing temperature and patterning of the nanostructures, easily obtainable homogeneity of precursor [14,15].…”