Effect of temperature and humidity on dielectric and impedance properties of K(Nb0.8Ta0.2)0.99Mn0.01O3 electroceramics

Abstract

We report the effect of humidity and temperature on the dielectric and impedance properties of lead-free potassium tantalum niobium oxide (KTN). It illustrates large dielectric constant ∼4500 at 1 kHz, low tangent loss in dry condition, which drastically changes under humidity condition. The nature and magnitude of dielectric constant and tangent loss were moderately different in both heating and cooling conditions. A series of phase transitions from rhombohedral to orthorhombic (below room temperature), and orthorhombic to tetragonal (∼185 °C) and tetragonal to Cubic (390 °C) have been obtained respectively over a wide range of temperature with a significant change in magnitude and nature in transition temperature during cooling mode. A detail transport properties have been carried out based on Impedance spectra, Modulus spectra, Nyquist Plot, and ac conductivity to establish a microstructure-property relation. The activation energy of the charge carriers determined that mainly electronic charge carriers contribute to transport properties in the low-temperature range while oxygen vacancies and cations near the high-temperature ferroelectric phase transition. The effect of moisture on room temperature capacitance, tangent loss, and impedance have been discussed.

Keywords

• ferroelectrics
• impedance
• ferroelectric phase transition (FPT)
• complex impedance
• spectroscopy (CIS)
• polarization