Effect of substitution and processing on the morphology and dielectric properties of Pr2/3Cu3Ti4O12 (PCTO) ceramic

Abstract

Low-cost, large dielectric constant, and resistivity materials have wide range of applications for radio frequency systems, flash memory devices to ferroelectric switches, and energy storage applications. The paper reports on the development and characterization of high-resistivity Pr_2/3Cu₃Ti₄O₁₂ (PCTO) ceramics developed by doping with Ca²⁺ and Sr²⁺ ions under various processing conditions. In particular, synthesis and growth were performed at 1173 and 1273 K resulting in significant difference in both electrical and morphological properties. To alter the distortion and polarity of ceramics, low concentration (0.15 mole fraction) of Ca²⁺ and Sr²⁺ hetero-valent ions with different size were substituted for Pr³⁺. The evolution and sizes of non-spherical, non-faceted grains altered to facet shapes due to changes in the anisotropy developed with increased copper concentration in the grains. The morphology analysis at these low processing temperatures revealed that grain growth occurs by engulfment of smaller grains by larger grains, necking process, and channel formation, with particles growing in nanometer size to greater than 10 µm and forming new layers on top of grains. The migration of copper-rich phases above 1173 K from boundaries to grains causes faceted morphology in both pure and substituted PCTO. Finally, by substituting Ca²⁺ and Sr²⁺ into the ceramics, altering the processing temperature, resistivity, and dielectric constant significantly increased. The substituted ceramics showed a higher dielectric constant at applied frequencies of 100‒100 000 Hz and did not vary at bias voltages of 50‒1000 mV, indicating no breakdown of the ceramics.