Temperature dependence of dielectric properties of sodium potassium niobate ceramics for different values of x (Na1-xKxNbO3)

Dielectric constant, loss tangent and electrical conductivity of Na1-xKxNbO3 (X = 0.08 and 0.17)(SPN) ceramic pellets have been measured at 10, 100 and 1000kHz frequencies and at temperature varying from room temperature to 425 degrees C. The dielectric constant increases with increase of temperature up to 400 degrees C at all the three frequencies, and thereafter, it decreases with further increase of temperature, i.e., it shows a structural transition at about 400 degrees C. The loss tangent also shows similar behaviour as dielectric constant shows. Some variations may be due to relaxation effects and impurities etc. around the sensitive transition region, which are seem to play prominent role in this soft mode region. Electrical conductivity increases with increase in temperature at all the three frequencies.