Influence of Calcination Kinetics Parameters on Synthesis of KNN Piezoelectric Ceramics

The current research was focused on synthesizing potassium sodium niobate (KNN) piezoelectric ceramics for the system (K۰.۴۸Na۰.۵۲) NbO۳   by high energy ball milling process for ۱۵h at the speed of ۳۰۰ rpm.  The blended nano-crystalline powder was calcined in conventional box furnace at ۷۰۰oC, ۸۰۰oC and ۹۰۰oC for duration of ۵h, ۷h and ۱۰h.  Diffraction result of calcine powder confirmed the formation of pure perovskite structure at ۹۰۰°C, ۷h along with the phase transformation from orthorhombic to tetragonal crystal structure but resulted in the formation of secondary phases at ۹۰۰°C, ۱۰h. Fourier Transmittance analysis was carried out for ۷۰۰°C, ۸۰۰°C and ۹۰۰°C to obtain the adsorption or emission of KNN nano powders and identified the stable crystal structure at ۹۰۰°C, ۷h. Hence optimized calcination parameters were   ۹۰۰°C, ۷h. The study of mass loss before and after calcination identified the decomposition of the carbon atoms into bicarbonates and completion of the chemical reaction. The study confirmed that calcination kinetics were time and temperature dependent. Morphology of the calcined powders revealed cubical structure with good compactness for ۹۰۰oC of ۷h calcination with the grain size in the range of ۶۵nm-۱۲۰nm.

کلیدواژه ها:

KNN ، High Energy ball milling ، Calcination kinetics ، Phase transformation ، Cubical crystal structure