Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating

Abstract

High demands on low-voltage electronics have increased the need for zinc oxide (ZnO) varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr6O11) based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr6O11 addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr6O11 from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr6O11 content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary.

Effect of erbium-calcium manganite doping on microstructure and electrical properties of zinc oxide based varistor ceramics

“…In this study, the effects of Er 2 O 3 mol%, sintering process (soaking temperature and time) on microstructure and electrical characteristics of (CaMnO 3 [7,10]. Thus, by the XRD (Fig.…”

“…However, with concern to produced low voltage varistor, Pr 6 O 11 start to study as alternative additive to produced low voltage varistor. Used of Pr 6 O 11 as answer to high volatility and reactivity in Bi 2 O 3 [5,[7][8]. Extensive study by [9] with introduced CaMnO 3 shows capability of perovskite structure onto low voltage application.…”

Conventional Sintering Effects on the Microstructure and Electrical Characteristics of Low-Voltage Ceramic Varistor

“…with large nonlinearity coefficients [47] and surpasses the results as reported by using ZnO-Bi 2 O 3 based and ZnO-Pr 6 O 11 based varistor [53,54]. The low-voltage nonlinearity originates as a result of higher concentration of manganese present at the grain boundary layer regions, being charge compensated by zinc vacancies [47].…”

Case Study about the Energy Absorption Capacity of Metal Oxide Varistors with Thermal Coupling

“…Apparently, this structure has no advantage, since each of the two varistors has "lost" one of the faces, used as heat dissipation surfaces. Instead, the assembly behaves like a dual-mass varistor, but traversed by an approximately two-fold lower current [17] (when an impulse is applied). If the two I(U) characteristics are different (in the present case very little different) the currents that will pass through the varistors will be different, the varistor with the lower UN threshold voltage will withstand the higher current (and hence a higher heating).…”

“…Apparently, this structure has no advantage, since each of the two varistors has "lost" one of the faces, used as heat dissipation surfaces. Instead, the assembly behaves like a dual-mass varistor, but traversed by an approximately two-fold lower current [17] (when an impulse is applied).…”