Thermal Decomposition and Possible Polymerization in KH_2AsO_4 Crystal at High Temperatures(Condensed Matter : Structure, Mechanical and Thermal Properties)

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概要

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• The high-temperature transformation of KH_2AsO_4 was studied by means of impedance spectroscopy, optical microscopy, differential thermal analysis, thermogravimetric methods. The dielectric constant showed a high-temperature anomaly around T_P = 185℃. The complex impedance spectra near T_P were fitted by superposition of two Cole-Cole types of relaxations. The fast component is interpreted by proton migration in the bulk, while the slow component is accounted for as a cluster formation due to breaking and reforming of the hydrogen bond at the surface. Upon heating above 185℃(T_P), the dark spots appeared at the surface and the their pattern grew up with increasing temperature and time under isothermal condition above 185℃. The thermal transformation which appears around T_P = 187℃ is endothermic in addition to showing weight loss. Our results show evidences that the high-temperature transformation of KH_2AsO_4 near T_P is not a structural phase transition, but an onset of thermal decomposition of KH_2AsO_4 into K_nH_2As_nO_3n+1 [probably, n ≫ 1, (KAsO3)_n] at reaction sites at the surface of crystal.

• 社団法人日本物理学会の論文
• 2002-11-15

著者

• PARK Jong-Ho

  Basic Science Research Institute, Pukyong National University

• Park J‐h

  Graduate Student Of Ibaraki University

• Park J‐h

  Basic Science Research Institute Pukyong National University

• Park J‐h

  Pukyong National Univ. Busan Kor

• PARK Jong-Ho

  Department of Physics, Pukyong National University

• Park Jong-ho

  Department Of Physics Inje University

関連論文

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• Phase Transition Dielectric Anomaly of PLZT Ceramic in the Temperature Range of 30-350℃
• Thermal Decomposition and Possible Polymerization in KH_2AsO_4 Crystal at High Temperatures(Condensed Matter : Structure, Mechanical and Thermal Properties)
• Physical Properties of CsH_2PO_4 Crystal at High Temperatures
• Phase Transition Dielectric Anomaly of PLZT Ceramic in the Temperature Range of 30-350℃
• Nature of the High-Temperature Dielectric Anomaly in TlH_2PO_4
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• Prediction of Flow Stress at 10^3/s for an Ultra Low Carbon Steel by the Kocks - Mecking Model
• Dielectric Study on the Low-Temperature Phase Transition of TlH_2 PO_4
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