As more and more people across walks of life turn to their mobile phones for performing lifestyle functions — listening to music, watching movies, ordering food, navigating new places, among others — and a public push towards electric vehicles (EVs) for transportation, finding effective materials for storing and managing energy is challenging.
Imagine smartphones that can charge in minutes and last days or electric cars that can travel longer distances on a single charge.
A recent study by researchers — Hodam Karnajit Singh, Prajna P Mohapatra, Subingya Pandey and Pamu Dobbidi — at IIT Guwahati has brought us closer to this reality by exploring the potential of a special kind of ceramic composite material. These are advanced materials engineered to have extraordinary electrical properties.
But it’s not just about storing more power. These materials also show fascinating dielectric relaxation behaviours — essentially, they can respond to changes in electric fields in ways that can be incredibly useful for electronic applications such as sensors or even in the development of stealth technology, by absorbing unwanted microwave signals.
How it’s made
At the heart of this research is the creation of a dense ceramic composite from a blend of two specific types of ferrites: M-type hexaferrite and an inverse spinel ferrite (NCZFO). When combined into the new composite material, it exhibits what scientists call “colossal permittivity.” Permittivity is a measure of how well a material can store electrical charge. Higher permittivity means more electricity can be stored, which is exactly what we need for better batteries and more efficient electronic devices.
However, creating these composites aren’t simple; it involves carefully mixing and heating the materials in a solid-state process — a method notable for its precision and control over material properties.
The researchers started off with precise weighing of pure barium carbonate (BaCO3), strontium carbonate (SrCO3), and iron oxide (Fe2O3) powders required for the hexaferrite phase.
The powders were then subjected to ball milling for 12 hours. After milling, the resultant slurry was dried through a slow heating process which were then calcined (the process in which the materials are heated to a high temperature in the absence or limited supply of air or oxygen). This step is crucial for initiating chemical reactions between the raw materials to form the hexaferrite phase.
The other ferrite — inverse spinel ferrite (NCZFO)— was also prepared using a solid-state reaction method. The proportions of nickel, cobalt, zinc, and iron precursors were carefully controlled, similar to the hexaferrite preparation.
The synthesised M-type hexaferrite and NCZFO were then combined in varying percentages (80–20 per cent, 60–40 per cent, and 40–60 per cent of hexaferrite to NCZFO, respectively) to explore the effects of different concentrations on the composite’s properties.
The mixed powders were ball-milled for an additional 15 hours to ensure uniform distribution of the two phases. The homogenised powder mixture was then pressed into circular plates using a hydraulic press. These plates were sintered at 1250°C for 3 hours. Sintering further densifies the material, which enhances the chemical bonds between the components and optimises the micro-structural properties crucial for achieving colossal permittivity.
The researchers varied the concentrations of each component to see how it affected the material’s properties. They discovered that adjusting these concentrations changed the material’s microstructure, including the size of the grains within the composite and the presence of tiny defects. These microscopic changes have a massive impact on how electricity is stored and flows through the material.
High permittivity materials can revolutionise energy storage solutions, making devices like capacitors far more efficient. Batteries that charge in a fraction of the current time, electric vehicles that need less frequent charging or even new types of sensors that can detect changes in the environment more accurately, becomes a possibility.
These materials could also lead to advances in telecommunications, enabling devices that can operate at higher frequencies, which are crucial for the next generation of wireless communications. In a world increasingly concerned with electromagnetic interference, these composites offer a promising solution. They could be used to shield sensitive equipment, from medical devices to military hardware, protecting them from interference and ensuring they operate reliably.
For a sustainable future
For the common man, this research might seem distant from everyday concerns. Yet, its implications are profound: In the not-too-distant future, this could mean electronics that are more durable, reliable and powerful.
It’s about more than just convenience; it’s about sustainability. Devices that charge faster and hold their charge longer are devices that consume less energy over their lifetime.
As we move towards a more electrified world efficient energy storage becomes crucial. These ceramic composites could play a vital role in this transition, helping to store energy more efficiently, whether it’s harvested from the sun, wind or waves.
