Influence of Sr2+ Doping, Temperature and Frequency on Dielectric Constant, Dielectric Loss Factor and AC Conductivity of Ammonium Zinc Chloride Crystal
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概要
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Ammonium zinc chloride (AZC) crystals doped with different strontium concentrations have been grown by the slow evaporation technique. Detailed temperature (300–450 K) and frequency (400–$10^{5}$ Hz) study of the dielectric constant ($\varepsilon$), loss factor ($\tan\delta$) and the ac conductivity ($\sigma_{\text{ac}}$) of the grown crystals has been carried out. Along the polar $b$-axis $\varepsilon$ increased gradually with increasing temperature showing clear peaks at the phase transitions. Thermal recycling decreased $\varepsilon$, inhibited the peak height, decreased its broadening but without shifting the transition points. However, Sr2+-doping causes a shift of the transition temperature towards lower values and a decrease in the $\varepsilon$-peak broadening and height. Relation between $1/\varepsilon$ and $T$ in the vicinity of the commensurate (C) to incommensurate (IC) phase transition revealed the validity of an equation similar to the Curie–Weiss law. Doping with Sr2+ in different concentrations causes a systematic change in the equation constants. Soliton pinning increased in the presence of Sr2+ leading to residual discommensurations (DC’s) in the C-phase. The dielectric constant decreased continually with increasing frequency for the undoped and Sr2+-doped samples. Doping with 0.144 wt% Sr2+ destroyed 25% of the C-phase, which means the possibility of having AZC crystal with reduced C-phase. $\sigma_{\text{ac}}$ increased with increasing frequency following a power law of the form $\sigma=\sigma_{\text{o}} f^{\text{s}}$. Conduction by hopping was found to be dominant in all phases of AZC and after doping with Sr2+ in different concentrations. Mechanism for DC formation and annihilation was also discussed.
- Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
- 2005-04-15
著者
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Gaffar Mohamed
Physics Department School Of Science And Engineering The American University In Cairo
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El-Fadl Abdel
Physics Department, Faculty of Science, Assiut University, Assiut 71516, Egypt
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Anooz Sand
Physics Department, Faculty of Science, Assiut University, Assiut 71516, Egypt
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Anooz Sand
Physics Department Faculty Of Science Assiut University
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El-fadl Abdel
Physics Department Faculty Of Science Assiut University