Hydrothermal synthesis of piezoelectric BaTiO₃ nanoparticles: a deep comparison between oven and microwave.

The Internet of Things is a society where we are connected to everyone and everything, a result from the constant technological evolution our world faces every day. This is possible through ferro- and piezoelectric based nano-based sensors, which are energetically self-sufficient but still require easier routes of production [1]. Barium titanate (BT) is a lead-free metal oxide with remarkable ferroelectric properties and a strong candidate to replace nowadays lead-based piezoelectric materials [2]. Initial production routes of BT nanostructures involved high temperatures and costs, such as solid-state reactions with calcinations steps, but a more recent approach, the hydrothermal synthesis, allows us to produce BT nanoparticles in a more controlled manner and at much lower temperatures [3]. In this work, we have produced BT nanoparticles by two distinctive hydrothermal methods: a conventional route made in an oven, and a microwave approach, in order to evaluate the better performing particles for piezoelectric and electronic applications. Synthesis parameters were kept the same between the procedures and produced particles were characterized by X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy. Furthermore, powders were compressed into pellets for evaluation using an LCR meter and piezoelectric response force microscopy (PFM). The microwave procedure allowed for a faster formation of the BT phase, especially at low synthesis durations (1h), while showing high degree of crystallinity and identifiable cubic nanoparticles. Regarding electrical measurements, analyzed pellets showed similar results between the two procedures.

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