Pressure sensitivity and dielectric properties of YBa₂Cu₃O_7+&/silicone rubber composite

Pressure sensitive superconductor/polymer composites were prepared using silicone rubber and high temperature superconductor YBa₂Cu₃O_{7 +δ}(YBCO) powder at different mass ratios. The piezoresistance and the dielectric properties of the composite samples at room temperature were measured. It was found that the resistance of all samples decreases exponentially with increasing pressure：application of different pressurees could result in a decease of 1～4 orders of magnitude in resistivity. Both resistivity and its sensitivity to external pressure vary with the superconductor filler content. The electrical resistivity was also measured as a function of temperature for samples from 300～50 K. The result shows that the change of resistivity is considerably larger. There are sharp decreases in the resistivity of superconductor/polymer composite samples below 90 K，but the sample of superconduction with zero resistivity was not found from 90～50 K. The dielectric content and dielectric loss of the composite at room temperature decrease with increasing frequency in the range from 1000 Hz to 5 MHz. It is found that both dielectric constant and dielectric loss are strongly dependent on the YBCO content. With increasing YBCO content，the dielectric constant and dielectric loss of all samples are larger.