Effect of RE3+ (RE = Eu, Sm) ion doping on dielectric properties of nano-wollastonite synthesized by combustion method

The nano-ceramic perovskite oxide Wollastonite (β-CaSiO3) doped with rare earth (RE) ions Eu³⁺and Sm³⁺ were synthesized by Low temperature solution combustion method, characterized by Powder XRD (X-ray Diffraction), FTIR(Fourier Transform Infrared Spectroscopy). The XRD studies revealed that there is a phase transition from β- to α-phase on doping with rare earth ions. The FTIR results showed that there is a dramatic stress on the Si-O bonds due to the effect produced by means of A-site vacancies resulted, on substitution of Eu³⁺ and Sm³⁺ in Ca2+ site. The particle size was estimated by TEM (Transmission Electron Microscopy), it was compared with the size determined by Scherrer´s formula. The SEM (Scanning Electron Microscopy) of β-CaSiO3 shows that it is a porous material containing agglomerated nanoparticles. The dielectric measurements for lower frequencies (10² Hz–10⁶ Hz) were performed for the undoped as well as doped with Eu³⁺ (3 mole %) and Sm³⁺(4 mole %). The measurements revealed that the undoped β-CaSiO3 shows high dielectric constant (54) and low dielectric loss (0.03) and low value of dielectric conductivity (of the order of 10–7mho cm) at 1MHz.frequency. However the dielectric constant (66) increased and dielectric loss (0.008) decreased by doping with the rare earth elements of atomic radii smaller than that of Calcium and an unusual observation is that the dielectric constant, dielectric loss and dielectric conductivity become equalized when β-CaSiO3 was doped with 3 mole% Eu³⁺ and 4 mole% Sm³⁺.