Gas Sensing Behavior of Porous ZnO Varistors Densified via Rate Controlled Sintering

1996 ◽  
Vol 431 ◽  
Author(s):  
Gaurav Agarwal ◽  
Robert F. Speyer
Keyword(s):  
Grain Size ◽  
Gas Sensor ◽  
Breakdown Voltage ◽  
Gas Sensing ◽  
Hydrogen Gas ◽  
Adsorbed Oxygen ◽  
Intergranular Porosity ◽  
Zno Varistor ◽  
Rate Controlled ◽  
Zno Varistors

AbstractA hydrogen gas sensor based on shift in breakdown voltage of a ZnO varistor was developed. Changes in rate controlled sintering schedules resulted in significant variations in microstructure. Microstructures showing more intergranular porosity and finer grain size demonstrated a comparatively more linear and broad response to H2 concentration. A mechanism for the shift in breakdown voltage based on adsorbed oxygen is suggested for this unique and potentially very useful sensor.

Effect of Ba Addition on Electrical Characteristics of Bi-Based ZnO Varistors

2010 ◽  
Vol 445 ◽  
pp. 241-244 ◽  
Author(s):  
Ai Fukumori ◽  
Masayuki Takada ◽  
Yuji Akiyama ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Breakdown Voltage ◽  
Electrical Characteristics ◽  
Zno Varistor ◽  
Electrical Degradation ◽  
Poor Tolerance ◽  
Zno Varistors ◽  
Molten Phase

With the goal of fabricating low-breakdown-voltage varistors, the effect of adding Ba to ZnO varistors on the ZnO grain size was investigated. Grain growth of ZnO could be markedly promoted by adding both Ba and Bi. The maximum grain size was approximately 150 μm and the minimum varistor voltage was approximately 12 V/mm. However, it had relatively poor tolerance characteristics for electrical degradation. It is speculated that when adding both Ba and Bi to a Mn–Co-added ZnO varistor, it is necessary to form the molten phases of Ba and Bi to promote grain growth of ZnO. It is also conjectured that the growth of ZnO grains is not promoted when Ba and Bi do not coexist in the molten phase because Ba forms compounds with Mn independently with the addition of small amounts of Bi.

Grain size control and gas sensing properties of ZnO gas sensor

2000 ◽  
Vol 66 (1-3) ◽  
pp. 277-279 ◽  
Author(s):  
Jiaqiang Xu ◽  
Qingyi Pan ◽  
Yu'an Shun ◽  
Zhizhuang Tian
Keyword(s):  
Grain Size ◽  
Gas Sensor ◽  
Gas Sensing ◽  
Size Control ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
Grain Size Control

Effect of Sintering Temperature on Electrical Properties of ZnO Varistor Ceramics

2012 ◽  
Vol 442 ◽  
pp. 31-34
Author(s):  
Chang Qi Xia ◽  
Qi Bin Liu ◽  
Mo He
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Leakage Current ◽  
High Voltage ◽  
Sintering Temperature ◽  
Voltage Gradient ◽  
Varistor Ceramic ◽  
Zno Varistor ◽  
Zno Varistors ◽  
Ceramic Sintering

To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, the effect of different sintering temperature (1135～1155 °C) on electrical properties of ZnO varistors were investigated. The experimental results show that with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. When the sintering temperature is at 1135 °C, the voltage gradient of varistor is up to 329V/mm, the leakage current is 8μA and the density is 96.4%. When the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%. Compared the results at 1135 °C with 1140 °C , it is found that the comprehensive electrical properties of ZnO varistors reach maximum at 1140 °C.

Continuous amperometric hydrogen gas sensing in ionic liquids

The Analyst ◽  
2018 ◽  
Vol 143 (17) ◽  
pp. 4136-4146 ◽  
Author(s):  
Yongan Tang ◽  
Jianxin He ◽  
Xiaoli Gao ◽  
Tianbao Yang ◽  
Xiangqun Zeng
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Real Time ◽  
Gas Sensor ◽  
Gas Sensing ◽  
High Sensitivity ◽  
Hydrogen Gas ◽  
Speed Accuracy

Continuous and real-time ionic liquid based hydrogen gas sensor with high sensitivity, selectivity, speed, accuracy, repeatability and stability.

Microchemistry of ZnO Varistors

1992 ◽  
Vol 50 (2) ◽  
pp. 1694-1695
Author(s):  
K. K. Soni ◽  
J. Hwang ◽  
V. P. Dravid ◽  
T. O. Mason ◽  
R. Levi-Setti
Keyword(s):  
Grain Boundaries ◽  
Multiple Roles ◽  
Grain Boundary Engineering ◽  
Ion Microprobe ◽  
Dopant Distribution ◽  
Important Ingredient ◽  
Zno Varistor ◽  
Zno Varistors ◽  
Zno Powder ◽  
The University

ZnO varistors are made by mixing semiconducting ZnO powder with powders of other metal oxides e.g. Bi2O3, Sb2O3, CoO, MnO2, NiO, Cr2O3, SiO2 etc., followed by conventional pressing and sintering. The non-linear I-V characteristics of ZnO varistors result from the unique properties that the grain boundaries acquire as a result of dopant distribution. Each dopant plays important and sometimes multiple roles in improving the properties. However, the chemical nature of interfaces in this material is formidable mainly because often trace amounts of dopants are involved. A knowledge of the interface microchemistry is an essential component in the ‘grain boundary engineering’ of materials. The most important ingredient in this varistor is Bi2O3 which envelopes the ZnO grains and imparts high resistance to the grain boundaries. The solubility of Bi in ZnO is very small but has not been experimentally determined as a function of temperature.In this study, the dopant distribution in a commercial ZnO varistor was characterized by a scanning ion microprobe (SIM) developed at The University of Chicago (UC) which offers adequate sensitivity and spatial resolution.

Effect of Grain Size on Strain in a Copper Oxide Nanofilm for Gas Sensing Applications

2019 ◽  
Vol 11 (5) ◽  
pp. 05040-1-05040-4
Author(s):  
Sumanta Kumar Tripathy ◽  
◽  
Sanjay Kumar ◽  
Divya Aparna Narava ◽  
◽  
...  
Keyword(s):  
Grain Size ◽  
Copper Oxide ◽  
Gas Sensing ◽  
Sensing Applications
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