The Influence of Terfenol-D Content on the Structure and Properties of Multiferroic Composites Obtained Based on...

In this work, three composite materials based on Terfenol-D and PZT-type material were obtained with a classic sintering method using a combination of 0-3 phases, where the ferroelectric phase was doped PZT material (P) and the magnetic phase was Terfenol-D (T). The percentage of P and T components in the composites was variable, i.e., 90% P/10% T (P90-T10), 70% P/30% T (P70-T30), and 50% P/50% T (P50-T50). Structural, microstructure, dielectric, and magnetic properties and DC electric conductivity of multiferroic composites were investigated. Chemical composition analyses and X-ray studies showed a decomposition of the composite compositions, forming additional phases, most of which contained rare earth elements and Fe. Microstructural SEM-BE (backscattering) images distinguished areas of bright intensity with a dominant ferroelectric phase and dark areas with a dominant magnetic element dominance. Despite the composition decomposition, the composite materials retained good dielectric and magnetic properties at room temperature. The highest stability of dielectric parameters was maintained by the P90-T10 composition with high values of permittivity ε = 570 at room temperature RT (ε_m = 7300 at the phase transition temperature T_m) and the lowest dielectric tangent loss (tanδ of 0.32 and 1.94 for RT and T_m, respectively). Increasing the Terfenol-D share in the composite causes a significant increase in dielectric tangent loss and electrical conductivity, a decrease in permittivity, and an increase in the degree of phase transition blurring. The magnetic properties for all P-T composite compositions at RT were preserved and were 0.31 emu/g, 1.60 emu/g, and 4.56 emu/g for P90-T10, P70-T30, P50-T50, respectively. For the M-H hysteresis loop at room temperature, the maximum magnetization increased from 1.17 emu/g for (P90-T10) to 15.18 emu/g for (P50-T50), while the coercive field decreased from 271.8 mT for P90-T10 to 9.7 mT for P50-T50. It is also interesting to maintain the high saturation of the M-H magnetic hysteresis loop in the composite with the lowest Terfenol-D content (P90-T10). The magnetic properties for all P-T composite compositions at room temperature were preserved and were 0.31 emu/g, 1.60 emu/g, and 4.56 emu/g for P90-T10, P70-T30, and P50-T50, respectively. For the M-H hysteresis loop at RT, the maximum magnetization increased from 1.17 emu/g for (P90-T10) to 15.18 emu/g for (P50-T50), while the coercive field decreased from 0.272 T for P90-T10 to 0.001 T for P50-T50. It is also interesting to maintain the high saturation of the M-H magnetic hysteresis loop in the composite with the lowest Terfenol-D content (P90-T10). Due to the tendency to combine with oxygen and the high electric conductivity of Terfenol-D, limiting its amount in the composite composition is appropriate. At 10% of Terfenol-D, the composite has good dielectric properties, and the magnetic parameters remain satisfactory.