Preparation and X-Ray diffraction, dielectric, and Mössbauer characterization of Co1 − xCuxCr2O4 ceramics

Co 1 − x Cu x Cr 2 O 4 (0 ≤ x ≤ 1) ceramic samples have been characterized by room-temperature X-ray diffraction and relative dielectric permittivity ɛ( T ) and loss tangent tanδ( T ) measurements (at frequencies from 0.1 to 200 kHz) in the range 100–350 K. The samples were shown to consist of spinel solid solutions with a cubic (0 < x < 0.53) or tetragonal (0.53 < x < 1) structure. Increasing the Cu content of the samples increases their tanδ and electrical conductivity and produces anomalies in the temperature dependences ɛ( T ) and tanδ( T ) due to dielectric relaxation processes. Co 1− x Cu x Cr 2 O 4 :0.01 57 Fe 2 O 3 samples were characterized by Mössbauer spectroscopy in the range 77–290 K and shown to be in a magnetically ordered state at 77 K.