Recently, we investigated the infrared spectra of a series of phases of this type, of composition Nd2_xCexCuO4-y and Nd2CuO4-xFx. In order to extend these studies and to obtain a more general picture of the vibrational behaviour of these materials, in this study we investigated the infrared spectra of a great number of phases containing different pairs of tetravalent and trivalent cations.