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Abstract
The thesis deals with the study of growing, identification and some physical properties of undoped ammonium zinc chloride (AZC) crystal and AZC doped with different concentrations of Sr2+ or Mn2+ ions. All crystals were growing by the slow evaporation method and the dopant concentration was measured by the atomic absorption technique. The crystal morphology changed considerably by doping and the unit cell parameters slightly changed with doping. Detailed temperature and frequency dependences of the dielectric constant ((), loss (tan() and ac conductivity ((ac) of the crystals have been carried out. Anomalous changes at the transition points connecting the AF, C, IC and N phases have been detected. In the vicinity of the C-IC phase transition the validity of Curie-Weiss law was found. The dc electrical conductivity as a function of temperature has been studied and the activation energy of conduction was calculated in each phase. from the current density (J) - field intensity (E) relationship according to the modified R-S equation the electronic mobility, the barrier height at the electrode-dielectric interface and the R-S constant were calculated. The results were discussed in the light of DC’s formation/annihilation. Optical absorption measurements near the absorption edge have been carried out. Analysis reveals that, at the absorption edges the type of transitions is the indirect allowed one for all crystals. The optical energy gap (Eg) at the room temperature decreased continuously with increasing Sr2+ or Mn2+ concentration. The refractive index (n), the extinction coefficient (K) were calculated as a function of photon energy. The validity of Cauchy-Sellimaier equation was checked and using the single-effective-oscillator model the moments of ((E) could be estimated. Exponential dependence of the absorption coefficient (() according to the Urbach rule was observed and the Urbach parameters were determined. The steepness parameter (() is strongly affected by doping. The effect of Gamma - or electron irradiation on optical parameters of the crystals has been investigated.