CaZrO₃ nanoparticles by the microwave assisted hydrothermal method

Full text: Perovskite ceramic with newly discovered mineral (2008, Russia) [1], the CaZrO₃ (CZ) presents sensor applications, photoluminescent emission at 450 and 700 nm, also shows a characteristic gap around 3.8 eV and can therefore be applied as a semiconductor and is thermally and chemically stable. This material can also be used, depending on the project work as capacitive or resistive sensor, the last one being the most conventional case because CZ shows good variation of resistivity according to the relative humidity of the environment into which it is inserted. Many recent studies indicate the synthesis of this material by various methods, including Pechini, solid state reaction and conventional hydrothermalization, however, there is no work that mentions the production of this material by the microwave assisted hydrothermal (MAH) method, which usually uses lower temperatures for the synthesis process. CZ nanoparticles were synthesized by the MAH method with maximum temperature of 140 °C and residence times of 20, 60, 100 and 160 min. Structural characterization by X-ray diffractometry and SEM were performed for the material synthesized and heat treated at 700 deg C, to 1000 deg C, where it was detected early crystallization phase lakargita (CZ) and portions of the metastable phase of ZrO₂ at 800 °C. Small portions of CaCO₃ are also identifiable. The material thus synthesized was subjected to thermal analysis showing the degradation of the carbonate phase of approximately 695 deg C where there is a small weight loss (6%). There is also an endothermic process at 85 deg C related to water loss, where there is a considerable amount of energy involved, showing the sensitivity of CZ of absorption and adsorption of water. Reference: [1] E. V. Galuskin, V. M. Gazeev, T. Armbruster, A. E. Zadov. Lakargiite CaZrO3: A new mineral of the perovskite group from the North Caucasus Kabardino- Balkaria, Russia, American Mineralogist. 93 (2008) 1903-1910.(author)