Colossal permittivity, electrical conductivity and ferromagnetic properties of pure TiO2: Mono and binary doping

Abstract

Advanced doping and binary doping techniques can open pathways to enabling rapid manufacture of high desired materials and structures. Herein, enhanced room temperature ferromagnetism with colossal dielectric constant were detected in pure, Fe doped, (Fe, Mn) and (Fe, Ni) codoped TiO2. High purity TiO2, Ti0.98Fe0.02O2, Ti0.96Fe0.02Mn0.02O2 and Ti0.96Fe0.02Ni0.02O2 compositions were synthesized by means of coprecipitation method. The XRD crystallographic planes of TiO2 compositions showed that mixed phases of rutile and anatase TiO2 were formed with absence of any impurities phases related to Fe, Mn or Ni oxides. Wide visible light band gap energy until 497 nm was achieved in TiO2 due to incorporation of (Fe, Mn) ions. Parallel relation between doping, codoping and particles size reduction was observed which reflects the strong influence of dopants on the grains growth of TiO2. Interestingly, Ti0.98Fe0.02O2, Ti0.96Fe0.02Mn0.02O2 and Ti0.96Fe0.02Ni0.02O2 compositions exhibit room temperature ferromagnetic behavior with constructive retentivity and coercivity values. Colossal dielectric permittivity (> 103) of 2335, 2327, 1857 and 1746 was detected for TiO2, Ti0.98Fe0.02O2, Ti0.96Fe0.02Mn0.02O2 and Ti0.96Fe0.02Ni0.02O2 structures, respectively. All TiO2 compositions reveal semiconducting-temperature performance and the electrical conductivity was enhanced due to (Fe, Mn) and (Fe, Ni) codoping. At low frequencies, the room temperature electrical conductivity of Ti0.96Fe0.02Mn0.02O2 and Ti0.96Fe0.02Ni0.02O2 is higher than that of TiO2 and Ti0.98Fe0.02O2. It seems that the defects chemistry and the charge carriers concentration of the pure TiO2 sample were affected by (Fe, Mn) and (Fe, Ni) codoping.