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 (K0.48Na0.52) NbO3   by high energy ball milling process for 15h at the speed of 300 rpm.  The blended nano-crystalline powder was calcined in conventional box furnace at 700oC, 800oC and 900oC for duration of 5h, 7h and 10h.  Diffraction result of calcine powder confirmed the formation of pure perovskite structure at 900°C, 7h along with the phase transformation from orthorhombic to tetragonal crystal structure but resulted in the formation of secondary phases at 900°C, 10h. Fourier Transmittance analysis was carried out for 700°C, 800°C and 900°C to obtain the adsorption or emission of KNN nano powders and identified the stable crystal structure at 900°C, 7h. Hence optimized calcination parameters were   900°C, 7h. 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 900oC of 7h calcination with the grain size in the range of 65nm-120nm.