Synthesis, characterization, and electrical studies on Cu-doped K2Ti6O13 lead-free ceramics: Role of defect associate dipoles

Pure and some copper doped (x = 0.01, 0.05, 0.1) ceramic specimens of K2Ti6O13 were synthesised using solid-state route. Lattice constants determined from room temperature XRD data revealed its single phase formation in a monoclinic symmetry. X-band EPR-data, recorded at RT, revealed the substitution of Ti4+ lattice sites by two different copper species corresponding to their distinct locally distorted environments. Dielectric data revealed the role of (Fe′Ti–VO)(Fe′Ti–VO)defect associate dipoles identified as low-field signals (g ∼ 5.43) in the EPR-spectra on the ferroelectric–paraelectric type phase transitions recognized in the ɛr(T) plots for all the compositions with distinct TC. Dielectric loss mechanism included space charge polarization, dipole orientation, and electrical conduction. Structural configuration was found to favour polaron conduction and impede the intratunnel ionic conduction. Moreover, electron-hopping conduction was dominant in the low-temperate region whereas intratunnel ionic conduction prevailed at higher temperatures.