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Ca has been partially substituted for Ba in the structure of BaTiO3 to investigate the influence on its dielectric relaxation time and piezoelectric properties. Ba1−xCaxTiO3 samples with x = 0.120, 0.140, 0.142, 0.144, 0.146, 0.148, 0.150, 0.152, and 0.160 were fabricated by the solid-state reaction method. The phase composition of the samples was identified by x-ray diffraction analysis. The impedance versus frequency characteristic in a range from 100 Hz to 2.5 MHz was measured at room temperature for all samples in both disk and cylinder shape. The results showed that Ca substitution considerably affected the piezoelectric properties of the fabricated samples. The piezoelectric properties were improved and optimized for x = 0.148, for which the relaxation time reached its minimal value. The relationship between the dielectric relaxation time and piezoelectric properties was found to be associated with structural phase competition as identified by high-resolution transmission electron microscopy analysis.

Cobalt ferrite nanoparticles (CFNPs) are emerging as a potential candidate for biomedical applications, such as magnetic hyperthermia therapy (MHT), due to their high saturation magnetisation (M S) and effective magnetic anisotropy constant (K eff) at the nanoscale. For MHT, heating efficiency depends considerably on applied AC magnetic field, particle diameter, and inter-particle interaction. Our study is aimed at developing a superparamagnetic nanosystem based on CFNPs with enhanced specific absorption rate (SAR) for advanced MHT. The CFNPs were synthesised using thermal decomposition of organometallic precursors. Transmission electron microscopy reveals a narrow size distribution of the CFNPs, with average particle sizes of 8 and 11 nm. Magnetic measurements showed high values of M S (~70 emu g−1) and K eff (2–3 × 106 erg cm−3). The ferromagnetic behaviour and strong interaction between particles at room temperature are also observed. Large SAR values of the CFNPs are achieved, which are superior to those reported previously in the literature. The high heating efficiencies of the present CFNPs make them a promising candidate for advanced MHT.

In this work the synthesis of thermo-sensitive polymer coated magnetic nanoparticles and their inductive heating have been studied. Poly (N-isopropylacrylamide-co-acrylic acid) (NA) polymers were first synthesized by emulsion polymerization of poly(N-isopropylacrylamide) (NIP) in water and followed by encapsulating magnetic nanoparticles (MNPs). As increasing the concentration of acrylic acid (AA), the lower critical solution temperature (LCST) increased, so that with 150% of AA (molar ratio) the LCST reached 42 °C, which is close to the temperature of hyperthermia treatment. Magnetization and ac susceptibility measurements were conducted to depict some characteristics of the NIP-MNPs and NA-MNPs that are related with the loss power. Attempts to analyze the rate of magnetic inductive heating were performed to show the Brownian relaxation origin of additional heat source created by the magnetite nanoparticles capped with thermosensitive polymers. Our results suggest that these thermo-sensitive polymer-coated magnetic nanoparticles show a potential for hyperthermia and drug delivery application.