Optimization and Tunability of Dielectric, Magnetic Properties, and Magnetoelectric Coupling of Cadmium Nickel Ferrite–BZT ME Composites

Lead-free magnetoelectric (ME) ceramic particulate composites of the type (y)Cd_1-xNi_xFe₂O₄ + (1–y) BaZr_0.2Ti_0.8O₃ (with weight fractions y = 0.1, 0.2, 0.3 and x = 0.1, 0.2, 0.3)were synthesized using the conventional solid-state reaction technique. Powder X-ray diffraction (XRD) confirmed the coexistence of ferrite and ferroelectric phases in the composites sintered at 1100 °C. Scanning electron microscopy (SEM) revealed detailed information on surface morphology, grain size, and porosity, with average grain sizes ranging from 1.08 to 3.80 µm. Energy-dispersive X-ray spectroscopy (EDX) was employed for elemental analysis and detection of possible foreign phases. Dielectric studies were carried out by measuring the dielectric constant (ε′) and dielectric loss tangent as functions of frequency (40 Hz–1 MHz) and temperature (30–650 °C) at four fixed frequencies (1 kHz, 10 kHz, 100 kHz, and 1 MHz).The dielectric constant showed a sharp decrease at lower frequencies, stabilizing to a constant value at higher frequencies. Magnetic characterization at room temperature exhibited well-defined M–H hysteresis loops, confirming the presence of an ordered magnetic structure in the ferrite–ferroelectric composites. The magnetoelectric effect, measured as a function of magnetic field intensity, displayed a linear variation. The static ME voltage coefficient [(dE/dH)H] was composition-dependent, with the maximum magnetoelectric voltage coefficient (α) recorded as 15.103 mV/cm·Oe for the composite with y = 0.2 and x = 0.3. The nearly constant magnetoelectric conversion factor further indicated that magnetostriction reached saturation during magnetic poling, resulting in a stable induced electric field in the ferroelectric phase.