SYNTHESIS AND CHARACTERIZATION OF Bi0.5(Na0.8K0.2)0.5TiO3-BASED CERAMICS OBTAINED THROUGH THE SOL-GEL METHOD

J. CAMARGO; R PARRA; L A RAMAJO; M CASTRO

Congreso; ICC7; 2018

Lead-based perovskites are widely used for actuators, sensors and transducers due to their excellent piezoelectric properties. However, the toxicity of lead for the environment and humans has been known for several decades. Consequently, many investigations are focused on finding substitutes for these materials. One candidate is the Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 solid solution, due to its interesting properties attributed to the presence of a morphotropic phase boundary in the composition Bi0.5(Na0.8K0.2)0.5TiO3. It is known, that the synthesis methods of nanopowders, such as the sol-gel process, have a special attention for the control of grain size. Consequently, this work focuses on the study of processing conditions and final properties of Bi0.5(Na0.8K0.2)0.5TiO3-based ceramics obtained by the sol-gel method.To obtain the desired phase, the reagents used were sodium acetate (CH3COONa), potassium acetate (CH3COOK), bismuth nitrate (Bi(NO3)3·5H2O) and titanium isopropoxide (C12H28O4Ti). The acetates and nitrate were dissolved, separately, in glacial acetic acid. The titanium isopropoxide was dissolved in a solution of isopropanol and acetic acid. The acetates and the nitrate were added one by one by dripping. After that, the mixture was stirring for one hour. Then, it was dried at 150 °C for 2 hours, and calcined at different temperatures (550 to 750 °C). The obtained powders were pressed uniaxially and sintered in the temperature range of 1000 to 1125 °C for 2 hours. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (ATG) and Raman spectroscopy. Density values of the sintered samples were measured by the Archimedes? method. Silver electrodes were painted on the plane-parallel faces and dielectric properties (LCR) were determined at temperatures (25 to 500 °C). Piezoelectric properties and electric hysteresis were also determined.Key words: piezoelectrics, Sol-Gel, electroceramics