Effect of impurities on the dielectric response of the charge-density wave inK0.3MoO3

We present the results of experiments in which the characteristics of the low-frequency relaxation of the charge-density wave (CDW) in ${\mathrm{K}}_{0.3}$ ${\mathrm{MoO}}_3$ ‘‘blue bronze’’ have been determined in the presence of weakly perturbing (Rb substituted for K) and strongly perturbing (W substituted for Mo) impurities. Both the mean relaxation time and static dielectric constant decrease strongly in the presence of the impurities. The temperature dependence of the CDW characteristics has been studied between approximately 25 and 90 K, and displays both similarities and differences from the results we obtained for the pure blue bronze. We discuss the results within the context of the classical model for CDW transport.