Effect of RE<sup>3+</sup> (RE = Eu, Sm) ion doping on dielectric properties of nano-wollastonite synthesized by combustion method

Abstract

The nano-ceramic perovskite oxide Wollastonite (β-CaSiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ) doped with rare earth (RE) ions Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> 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 Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> 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-CaSiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> shows that it is a porous material containing agglomerated nanoparticles. The dielectric measurements for lower frequencies (10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Hz–10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> Hz) were performed for the undoped as well as doped with Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> (3 mole %) and Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> (4 mole %). The measurements revealed that the undoped β-CaSiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> 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-CaSiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> was doped with 3 mole% Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and 4 mole% Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> .