Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob

This thesis describes the effects of Ca2+ and Mg2+ substitution on oxygen sensing properties of hot spot-based Eul23 rods. (Eu1-xCax)Ba2Cu3O7-δ (x=0-0.5) and (Eu1-yMgy)Ba2Cu3O7-δ (y=0.05)ceramics were synthesized from oxide powders using the standard solid state method and fabricated into short rods...

Full description

Saved in:

Bibliographic Details
Main Author:	Yaacob, Siti Azwani
Format:	Thesis
Language:	English
Published:	2013
Subjects:	Detectors Sensors Sensor networks
Online Access:	https://ir.uitm.edu.my/id/eprint/45660/1/45660.pdf
Tags:	Add Tag No Tags, Be the first to tag this record!

id	my-uitm-ir.45660
record_format	uketd_dc
spelling	my-uitm-ir.456602022-11-10T08:33:20Z Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob 2013 Yaacob, Siti Azwani Detectors. Sensors. Sensor networks This thesis describes the effects of Ca2+ and Mg2+ substitution on oxygen sensing properties of hot spot-based Eul23 rods. (Eu1-xCax)Ba2Cu3O7-δ (x=0-0.5) and (Eu1-yMgy)Ba2Cu3O7-δ (y=0.05)ceramics were synthesized from oxide powders using the standard solid state method and fabricated into short rods. For unsubstituted x=0 rod the I-V behavior after formation of hot spot showed decreasing output current with increasing voltage under different pO2 concentration. However, for Ca�substituted rods, after appearance of a visible hot spot, a constant current plateau in the I-V curve was formed. The output current response of the rod in periodically changing pO2 between 20% and 100% showed improved stability and reproducibility for x=0.1, x-0.4 and x=0.5 compared to x=0.2 and x=0.3. Improved oxygen absorption and desorption time was observed for (Eu1-xCax)Ba2Cu3O7-δ (x=0.1, 0.4, 0.5) compared to the unsubstituted rod. Among the Ca-substituted samples, the x=0.4 rod produces oxygen absorption and desorption time of 64.5 s and 93.1 s, respectively. On the other hand, for Mg-substituted rods I-V behavior after formation of hot spot showed a negative slope. Faster absorption time of 3.0 s and desorption time of 6.9 s were observed for y=0.4 compared to other Mg-substituted rods. The improved output current stability, reproducibility and response time is suggested to be due to changes in oxygen activation energy and increased hole concentration as a result of Ca2+/Mg2+ substitutions. The Mg-substituted rods showed better performance compared to Ca-substituted rods possibly due to higher porosity and vacancy concentration. However, the difference in PTCR behavior for the same substitution level between Ca-substituted and Mg-substituted rods is suggested to be due to the differences in ionic size of Ca2+ andMg2+ which caused differences in reduction of oxygen activation energy. For the unsubstituted and Mg-substituted series, the relation between output current and pO2 shows a good agreement with the ideal case of oxygen excess material, derived from the mass action law. 2013 Thesis https://ir.uitm.edu.my/id/eprint/45660/ https://ir.uitm.edu.my/id/eprint/45660/1/45660.pdf text en public masters Universiti Teknologi MARA Faculty of Applied Sciences Yahya, Ahmad Kamal Hayati
institution	Universiti Teknologi MARA
collection	UiTM Institutional Repository
language	English
advisor	Yahya, Ahmad Kamal Hayati
topic	Detectors Sensors Sensor networks
spellingShingle	Detectors Sensors Sensor networks Yaacob, Siti Azwani Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob
description	This thesis describes the effects of Ca2+ and Mg2+ substitution on oxygen sensing properties of hot spot-based Eul23 rods. (Eu1-xCax)Ba2Cu3O7-δ (x=0-0.5) and (Eu1-yMgy)Ba2Cu3O7-δ (y=0.05)ceramics were synthesized from oxide powders using the standard solid state method and fabricated into short rods. For unsubstituted x=0 rod the I-V behavior after formation of hot spot showed decreasing output current with increasing voltage under different pO2 concentration. However, for Ca�substituted rods, after appearance of a visible hot spot, a constant current plateau in the I-V curve was formed. The output current response of the rod in periodically changing pO2 between 20% and 100% showed improved stability and reproducibility for x=0.1, x-0.4 and x=0.5 compared to x=0.2 and x=0.3. Improved oxygen absorption and desorption time was observed for (Eu1-xCax)Ba2Cu3O7-δ (x=0.1, 0.4, 0.5) compared to the unsubstituted rod. Among the Ca-substituted samples, the x=0.4 rod produces oxygen absorption and desorption time of 64.5 s and 93.1 s, respectively. On the other hand, for Mg-substituted rods I-V behavior after formation of hot spot showed a negative slope. Faster absorption time of 3.0 s and desorption time of 6.9 s were observed for y=0.4 compared to other Mg-substituted rods. The improved output current stability, reproducibility and response time is suggested to be due to changes in oxygen activation energy and increased hole concentration as a result of Ca2+/Mg2+ substitutions. The Mg-substituted rods showed better performance compared to Ca-substituted rods possibly due to higher porosity and vacancy concentration. However, the difference in PTCR behavior for the same substitution level between Ca-substituted and Mg-substituted rods is suggested to be due to the differences in ionic size of Ca2+ andMg2+ which caused differences in reduction of oxygen activation energy. For the unsubstituted and Mg-substituted series, the relation between output current and pO2 shows a good agreement with the ideal case of oxygen excess material, derived from the mass action law.
format	Thesis
qualification_level	Master's degree
author	Yaacob, Siti Azwani
author_facet	Yaacob, Siti Azwani
author_sort	Yaacob, Siti Azwani
title	Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob
title_short	Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob
title_full	Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob
title_fullStr	Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob
title_full_unstemmed	Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob
title_sort	effect of divalent ca2+ and mg2+ substitutions on oxygen sensing properties of hot-spot based (eu1-xcax)ba2cu3o7-δ and (eu1-ymgy)ba2cu3o7-δ ceramic rods / siti azwani yaacob
granting_institution	Universiti Teknologi MARA
granting_department	Faculty of Applied Sciences
publishDate	2013
url	https://ir.uitm.edu.my/id/eprint/45660/1/45660.pdf
_version_	1783734742513876992

Effect of divalent Ca2+ and Mg2+ substitutions on oxygen sensing properties of hot-spot based (Eu1-xCax)Ba2Cu3O7-δ and (Eu1-yMgy)Ba2Cu3O7-δ ceramic rods / Siti Azwani Yaacob

Similar Items