Structural and dielectric properties of Pb0.91(La,K)0.09(Zr0.65Ti0.35)0.9775O3 ceramics

Potassium-modified polycrystalline samples of PLZT, Pb0.91(La1 − z/3Kz)0.09(Zr0.65Ti0.35)0.9775O3 [z = 0.0, 0.1, 0.3, 0.5, 0.7], were prepared using sol-gel technique. X-ray diffraction (XRD) of these compounds show that they can be formed in single phase at 800 °C. Pellets prepared from the above powders were sintered at 1100 °C. Detailed studies of the dielectric constant (ε) and loss tangent (tan δ) of the compounds at different frequencies (400 Hz to 10 kHz) at room temperature (RT) and temperature (RT to 350 °C) suggest that the compounds undergo ferroelectric phase transition of diffuse-type on increasing K-concentration. Analysis of diffuseness of these compounds gives a value close to 2, which indicates the presence of higher degree of disorder in PLZT substituted by K. The dielectric constant (ε) is found to increase initially and then to decrease with increasing K concentration.