Wei-Yean Howng

EFFECT OF DEFECT STRUCTURE ON GAS SENSITIVITY OF LACRO3

The isopropyl alcohol gas sensitivity of LaCrO{sub 3} at 250{degree}C is found to depend on the amount of TiO{sub 2} content and cation stoichiometric ratio of the sample. The gas sensitivity enhancement is related to the defect structure and electrical conduction behavior of {ital p}-type donor-doped semiconductive oxides. The high resistivity coupled with the increasing point defects by the donor dopants are responsible for the high gas sensitivity of TiO{sub 2} doped LaCrO{sub 3}. It is believed that the positively charged ionic-type defects created by dopants act as trapping sites to adsorb oxygen. {copyright} {ital 1996 Materials Research Society.}

High‐frequency properties of superconducting Y‐Ba‐Cu‐oxide thin films

rf and microwave properties of superconducting YBa2Cu3O7−x thin films were measured and analyzed using a coplanar resonator structure. The films were developed by sequential electron‐beam evaporation of the metals followed by postanneal processing. dc properties of the films were obtained from resistance‐temperature and current‐voltage measurements to evaluate the transition temperature and current densities. High‐frequency properties were measured from 70 to 10 K and in the frequency range 1–3 GHz to determine the film characteristics as compared to pure copper films on the same substrates.