This paper deals with the application of ZnO varistors-an area which has not been treated in a systematic way in the literature. The paper starts with a brief description of the fundamental properties comprising the electrical behavior as well as the physics, chemistry, and microstructure of the varistor. These properties then form the basis for defining the application parameters that are directly related to the nonlinear current-voltage characteristics of the varistor. This paper provides a detailed description of these parameters and their relation to microstructure and the processing of the varistor. Finally, a discussion is presented on the reliability of the varistor by considering a grain-boundary defect model which explains both the instability and the stability under use conditions. [

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We are developing large-area, thick, structured CsI(Tl) imaging sensors for a wide variety of X-ray imaging applications. Recently we have fabricated structured CsI(Tl) scintillators ranging from 30 µm (16 mg/cm 2) to 2000 µm (900 mg/cm 2) in thickness and up to 15 x 15 cm 2 in area. Even 2000-µm-thick film showed well-controlled columnar growth throughout the film. Material characterization confirmed that the film is crystalline in nature and that the stoichiometry is preserved. To improve the spatial resolution of thick films, post-deposition treatments were performed. The effect of these treatments on film characteristics was quantitatively evaluated by measuring signal output, modulation transfer function [MTF(f)], noise power spectrum [NPS(f)], and detective quantum efficiency [DQE(f)]. The data show that by proper film treatments, the film DQE(f) can be improved.

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