Very low loss tangent, high dielectric and non-ohmic properties of Ca_1−1.5xPr_xCu₃Ti₄O₁₂ ceramics prepared by the sol–gel process

In this work, Ca_1−1.5xPr_xCu₃Ti₄O₁₂ (0.00, 0.02, 0.04 and 0.06) ceramics were prepared by the sol–gel process. Very low loss tangent (tanδ) ∼0.016–0.022 and high dielectric constant (ε ^′) ∼6174–8469 with temperature coefficients less than ±15% over the temperature range of −75 to 135 °C were observed in all Pr³⁺-doped CaCu₃Ti₄O₁₂ ceramics. ε ^′ decreased with increasing Pr³⁺ ion due to the decrease of oxygen vacancies and grain size, resulting from the substitution of small ionic radius Pr³⁺ ion in the structure. X-ray absorption near edge spectroscopy (XANES) confirmed the decrease of Ti³⁺/Ti⁴⁺ and Cu⁺/Cu²⁺ ratios with increasing Pr³⁺ ions. In addition, all Ca_1−1.5xPr_xCu₃Ti₄O₁₂ ceramics displayed non-linear characteristics. Non-linear coefficient (α) and breakdown field (E _b) of all ceramic samples can be enhanced by Pr³⁺ doping with the highest α value of ~14.74 and E _b of ~5640 V/cm⁻¹ in sample with x = 0.02. Effect of Pr³⁺ doping on phase composition and microstructure of samples were studied using X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-rays spectroscopy.