Temperature dependence of the indirect band gap, steepness parameter and related optical constants of [Kx(NH4)1-x]2ZnCl4 mixed crystals

被引：15
作者：
Abu El-Fadl, A. [1 ]
Soltan, A. S. [1 ]
Shaalan, N. M. [1 ]
机构：
[1] Assiut Univ, Fac Sci, Dept Phys, Assiut 71516, Egypt
来源：
OPTICS AND LASER TECHNOLOGY | 2007年 / 39卷 / 07期
关键词：
K-x(NH4)(1-x)](2)ZnCl4 mixed crystals; optical energy gap;
D O I：
10.1016/j.optlastec.2006.12.004
中图分类号：
O43 [光学];
学科分类号：
070207 ; 0803 ;
摘要：
Optical transmittance measurements near the absorption edge of [K-x(NH4)(1-x)](2)ZnCl4 mixed crystals, where x = 0.00, 0.232, 0.522, 0.644, 0.859 and 1.00, are reported over 276-350 K range. Analysis reveals that the type of transition is the indirect allowed one. The absorption edge shifted towards lower energy with increasing temperature. It is shown that [K-x(NH4)(1-x)](2)ZnCl4 mixed crystals with x <= 0.644 reveal a phase transition at 319 K, this phase disappeared at high concentrations of K+ ions. The steepness parameter is given, its value is used to estimate the temperature dependence of the indirect energy gap. In the region of the absorption edge, the absorption coefficient obeys Urbach's rule. Urbach parameters are investigated as a function of temperature. (c) 2007 Elsevier Ltd. All rights reserved.
引用
收藏
页码：1310 / 1318
页数：9
相关论文
共 31 条
[1]   Influence of cationic substitution on lattice constants and optical characterization in solution grown mixed crystals of potassium-ammonium zinc chloride [J].
Abu El-Fadl, A. ;
Soltan, A. S. ;
Shaalan, N. M. .
CRYSTAL RESEARCH AND TECHNOLOGY, 2006, 41 (10) :1013-1019
[2]  
ABULELFADL A, 1998, EUR PHYS J-APPL PHYS, V4, P5
[3]   EXPERIMENTAL STUDIES OF STRUCTURALLY INCOMMENSURATE CRYSTAL PHASES [J].
CUMMINS, HZ .
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 1990, 185 (5-6) :211-409
[4]  
Dunja I., 1991, J PHYS CHEM SOLIDS, V52, P915
[5]  
DVORAK V, 1992, PHYS STATUS SOLIDI B, V107, P1225
[6]   Temperature dependence of the optical band gap of nearly perfect K2ZnCl4 single crystals in the ferroelectric phase [J].
El-Korashy, A ;
Abu El-Fadl, A .
PHYSICA B, 1999, 271 (1-4) :205-211
[7]   Optical studies of K2ZnCl4 single crystals doped with Cs+ in the ferroelectric phase [J].
El-Korashy, A ;
Abu El-Fadl, A ;
El-Zahed, H .
PHYSICA B, 2001, 304 (1-4) :437-443
[8]   Electric, dielectric and optical studies of the lower phase transition of lithium ammonium sulphate single crystals [J].
Gaffar, MA ;
Abu El-Fadl, A .
PHYSICA B-CONDENSED MATTER, 1999, 262 (1-2) :159-169
[9]   Optical absorption spectra and related parameters of ammonium zinc chloride crystal in the antiferroelectric and commensurate phases [J].
Gaffar, MA ;
Abu Ei-Fadl, A ;
Bin Anooz, S .
CRYSTAL RESEARCH AND TECHNOLOGY, 2003, 38 (09) :798-810
[10]  
GAFFAR MA, 2003, PHYS STATUS SOLIDI B, P1
1234