Structural study of the role of defects on the CDW instabilities of quasi-one-dimensional conductors

We present an x-ray study of the pinning of charge density waves (CDWʹs) in organic and inorganic materials. X-ray diffuse scattering experiments performed on doped crystals allow to obtain informations about the CDW coherence lengths, the local order of the impurities and the coupling between the CDWʹs and the defect position. In organic compounds, we give evidence of strong pinning. In the V-doped blue bronze, we show the existence of defect density waves associated to the CDW. In the Ti-doped transition metal trichalcogenure NbSe3, preliminary results concerning the strong pinning of the q1 CDW are reported.