Electrocaloric effect (ECE) in two ferroelectric liquid crystalline (FLC) materials has been evaluated by mean of two indirect characterization methods: the photopyroelectric (PPE) technique and the polarization current reversal one. The obtained results show a good correspondence of the adiabatic temperature change associated with the ECE evaluated from both methods. This validates the possibility to use the PPE technique to investigate the ECE in FLCs. This study also demonstrates that FLCs can be used as electrocaloric material. More particularly, it shows that as for their solid homologous, liquid crystals displays more pronounced ECE in the vicinity of a first order transition than that measured near to second-order one.

By means of the photopyroelectric method, we indirectly investigate the electrocaloric effect in polar materials by measuring the pyroelectric coefficient and the volumic heat capacity, as function of temperature. The influence of the heat capacity as function of the temperature on electrocaloric measurements is discussed. Measurements were performed on TriGlycine Sulfate single crystal. The compound showed a Δ T value of about 0.3 K upon a field change of 0.3 MV m ⁻¹ near it’s Curie temperature at 49 °C. Compared with repolarization current method where usually heat capacity is assumed as a constant value, the proposed technique provides an accurate way of calculating adiabatic temperature change of a ferroelectric material.

The electrocaloric heat production in \(\hbox {BaTiO}_3\)-based multilayer ceramic capacitors with Y5V specification was measured in a direct way by means of an adiabatic calorimeter setup. Applying an electric field of 30 \(\hbox {MV}\,\hbox {m}^{-1}\) is found to result in a heat release of 0.94 \(\hbox {J}\,\hbox {g}^{-1}\) and an electrocaloric temperature change of 0.46 K, in good agreement with direct results in previous studies.

Nanocomposite polymer films are a very diverse research field due to their many applications. The search for low-cost, versatile methods, producing regulated properties of the final products, has thus become extremely relevant. We have previously reported a bulk-scale process, dispersing granulated metal oxide nanoparticles, of both unary and multi-component nature, in a low-density polyethylene (LDPE) polymer matrix, establishing a reference in the produced films’ optical properties, due to the high degree of homogeneity and preservation of the primary particle size allowed by this method. In this work, unmodified, free-standing particles, namely zinc oxide ($ZnO$), titanium dioxide ($Ti{O}_2$), aluminum oxide ($A{l}_2{O}_3$), and silicon dioxide ($Si{O}_2$) are blended directly with LDPE, and the optical properties of the fabricated films are compared to those of films made using the granulation process. The direct blending process evidently allows for control of the secondary particle size and ensures a homogeneous dispersion of the particles, albeit to a lesser extent than the granulation process. Despite the secondary particle size being comparatively larger than its granulated counterpart, the process still provides a regulated degree of deagglomeration of the free-standing oxide particles, so it can be used as a low-cost alternative. The regulation of the secondary particle size tunes the transmission and reflection spectra, in both unary and mixed oxide compositions. Finally, the direct blending process exhibits a clear ability to tune the energy band gap in mixed oxides.