Preparation and Dielectric Properties of K1/2Na1/2NbO3 Ceramics Obtained from Mechanically Activated Powders

Abstract

Alkaline based materials have been considered as a replacement for environmentally harmful Pb(Zr,Ti)O3 (PZT) electro-ceramics. In this paper, the K1/2Na1/2NbO3 (KNN) ceramics were prepared in a three stage process: first Nb2O5, Na2CO3, and K2CO3 were milled in a high energy mill (shaker type) for different periods, between 25 h and 100 h, consecutively a solid state reaction was carried out at 550 °C. Finally, the uniaxially pressed samples were sintered at 1000 °C. The reaction temperature is lower for mechanically activated powders than in the case of the conventional solid-state method. The ceramic samples, prepared from the mechanically activated powders, were investigated by dielectric spectroscopy. The influence of the duration of the mechanical activation on the properties of the ceramic materials, e.g., ceramic microstructures, phase transition temperatures, character of the temperature dependences of dielectric permittivity, are discussed.

Thermal Stability and Non-Linear Optical and Dielectric Properties of Lead-Free K0.5Bi0.5TiO3 Ceramics

“…Table 5 compiles the results for KBT ceramics [45,49] and other commonly used ferroelectrics [87,88] in terms of the maximal relative permittivity (ε m ) and relative permittivity at ambient conditions (ε RT ). One can conclude that excellent dielectric properties characterize the KBT-24h specimen regarding the previously reported lead-bearing PbTiO 3 material, lead-free Na 0.5 Bi 0.5 TiO 3 ceramic, and even the K 0.5 Bi 0.5 TiO 3 analogue [45,49].…”

“…Several studies were issued regarding the effects of technological conditions on selected physicochemical properties of manufactured materials. For example, an exciting article concerning the mechanosynthesis of lead-free K 0.5 Na 0.5 NbO 3 ceramics was recently published [88], where only milling time was adjusted in the technological process. A high-energy mill was used for K 0.5 Na 0.5 NbO 3 synthesis [88], while in the present work, a significant improvement in dielectric properties was gained by using the planetary ball mill.…”

“…For example, an exciting article concerning the mechanosynthesis of lead-free K 0.5 Na 0.5 NbO 3 ceramics was recently published [88], where only milling time was adjusted in the technological process. A high-energy mill was used for K 0.5 Na 0.5 NbO 3 synthesis [88], while in the present work, a significant improvement in dielectric properties was gained by using the planetary ball mill. This is important since the ferroelectrics industry should conform to synthesis processes for the large-scale production of lead-free materials.…”