Abstract
This paper investigates the temperature dependence of microwave surface resistance (RS) of YBa2Cu3O7-x (YBCO) thin films with different microstructures at 10 GHz, using a coplanar resonator technique. YBCO thin films with different grain sizes were obtained as a result of changing the quenching procedure after film deposition by dc sputtering. The value of RS was found to vary with varying surface morphology and can be explained by the coupled grain model (CGM) when a temperature-dependent grain boundary resistance (R) is used. The temperature (T) dependence of R is given by R=R0+C(T/TC)2T, where TC is the superconducting critical temperature, and R0 and C are the fitting parameters, depending on the properties of each sample.