Enhanced dielectric response of Gd2Ti2O7 nanoparticles in SiO2 matrix

• Dielectric constant (ɛ′) of Gd2Ti2O7–SiO2 nanocomposite (studied for the first time) ≫ ɛ′ of Gd2Ti2O7 single-crystal.
• Incomplete diffuse phase transition (DPT) observed near room temperature (RT) with lossy like dielectric P(E) loop at RT.
• Dielectric relaxation near DPT arises from thermally activated oxygen ion vacancy (OIV) in Gd2Ti2O7 nanoparticles.
• Frequency activated conductivity observed in DPT regime may be related to small polaron hopping at the OIV sites.

Dielectric properties of Gd2Ti2O7 nanopaticles in SiO2 matrix are remarkably different in comparison with the Gd2Ti2O7 single crystal. Gd2Ti2O7–SiO2 nanocomposite exhibits significant increase in the dielectric constant (ɛ′) for smaller Gd2Ti2O7 nanopaticles (GdT900). ɛ′(T) behavior suggests diffuse phase transition (DPT) near room temperature (RT). The estimated value of the diffuseness exponent (γ) related to DPT is 1.35 for GdT900, indicating an incomplete DPT. The dielectric relaxation near DPT has been associated with the thermally activated oxygen vacancies. The P(E) loops for GdT900 near RT are slim with low values of remnant polarization (Pr ∼0.15 μC/cm2) and coercive field (Ec ∼ 0.85 kV/cm). Nyquist plot for GdT900 indicates that Gd2Ti2O7 nanopaticles play dominant role in electrical conduction. The frequency activated behavior of ac conductivity in the DPT regime suggests that the conduction is due to hopping of bound charge carriers like small polarons.

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