Results 181 to 190 of about 2,258 (200)

Varistor-capacitor characteristics of ZnO ceramics

Journal of Materials Science, 1986
Electrical properties of ZnO ceramics quenched from several temperatures during the cooling down from sintering temperature were correlated with microstructural changes. Barrier parameters were determined and their variation was interpreted under the assumption that measured donor densities were due to extrinsic donor defects segregated at grain ...
P. Q. Mantas, A. M. R. Senos, J. L. Baptista   +2 more
openaire   +1 more source

Intrinsic defects in ZnO varistors

Journal of Applied Physics, 1983
Theoretical calculations are presented for equilibrium concentrations of zinc and oxygen vacancies in ZnO. Results are presented at the sintering temperature, and also at room temperature. Theoretical calculations of reaction constants show that the intrinsic donor is the oxygen vacancy, rather than the zinc interstitial.
openaire   +1 more source

Ceramic varistors based on ZnO–SnO2

Journal of the European Ceramic Society, 2004
Abstract Model ceramic varistor formulations based on 98% ZnO–SnO2 (plus 2% oxides of Bi, Co and Mn) were prepared by conventional powder processing routes; specimens were sintered at 1150–1275 °C. The product density increased with SnO2 content, but decreased with increase in sintering temperature.
A. Anastasiou, M.H.J. Lee, C. Leach, R. Freer   +3 more
openaire   +1 more source

Different degradation processes in ZnO varistors

Ceramics International, 1996
Degradation of ZnO-based varistors has been attributed to ion migration in the depletion layers at intergrains. Experiments can then be explained as the result of the deformation of Schottky barriers present in the grain boundaries. However, the simple lowering of the barriers is not consistent with the observed results. We found that ion migration can
M.S. Castro, C.M. Aldao
openaire   +1 more source

Preparation of ZnO-glass varistor from tetrapod ZnO nanopowders

Materials Science and Engineering: B, 2002
Abstract Varistors based on ZnO–lead zinc borosilicate glass were prepared from tetrapod ZnO nanopowders, every one of which had four needle-like legs and each one was about 20 nm or less in diameter and from several hundreds of nanometers to several micrometers in length by the method of direct co-sintering synthesis of oxides instead of adding ...
Wu Jun, Xie Changsheng, Bai Zikui, Zhu Bailin, Huang Kaijin, Wu Run   +5 more
openaire   +1 more source

ZnO varistors for liquid crystal displays

Journal of Applied Physics, 1982
ZnO varistors are excellent materials for multiplexing dichroic liquid crystal displays. We describe here the development of varistor materials tailored for this application. The varistors are large (∼25 cm diameter), uniform, and have relatively low dielectric constant.
Lionel M. Levinson, Donald E. Castleberry, Charles A. Becker   +2 more
openaire   +1 more source

Photoluminescence study of ZnO varistor stability

Journal of Electronic Materials, 1995
Photoluminescence (PL) measurements were carried out on commercial ZnO varistor samples that were electrically stressed and/or annealed at different temperatures. Changes in the intensity of green and yellow luminescence centers were studied as a function of annealing treatment.
M. S. Ramanachalam, A. Rohatgi, W. B. Carter, J. P. Schaffer, T. K. Gupta   +4 more
openaire   +1 more source

ZnO varistors from intensively milled powders

Journal of the European Ceramic Society, 2007
Abstract Two ways of application of intensive milling in ZnO varistors processing were compared. First was intensive milling of mixture of previously prepared constituent phases. In this case, intensive milling was applied only to obtain highly activated nanocrystalline varistor powder mixtures.
Zunic, M., Brankovic, Z., Bernik, S., Goes, M. S., Brankovic, G.   +4 more
openaire   +2 more sources

Defects and degradation in ZnO varistor

Applied Physics Letters, 1996
A systematic study of the defects in ZnO has been performed. The two commonly observed levels (L1, L2), located at around 0.15 and 0.24 eV under the conduction band, have been identified as native defects. The deep level transient spectroscopy depth profiling technique is applied on multilayer-chip-type ZnO varistors to determine the distribution ...
Wei-I Lee, Ruey-Ling Young
openaire   +1 more source

Microwave Sintering of ZnO Varistor Ceramics

MRS Proceedings, 1992
ABSTRACTZnO varistors are electronic ceramics whose electrical behavior is dominated by grain boundary effects. A careful evaluation of the effect of microwave sintering compared to conventional sintering revealed no significant differences between varistor devices processed by these two methods.
Lionel M. Levinson, Holly A. Comanzo, William N. Schultz   +2 more
openaire   +1 more source