Study of the densification, mechanical and magnetic properties of Ni–Zn ferrites sintered in a solar furnace

Solar sintering is a technology that enabled the production of a dense ceramic body, thereby improving the functional and structural properties of ceramic and metals. In this experimental work, the density, microstructure, mechanical and magnetic properties of NiZn ferrites sintered in a solar furnace and in a conventional electrical furnace were compared. Ni–Zn ferrites samples (fabricated by uniaxial pressing) were sintered in a Solar Furnace at Plataforma Solar de Almería (PSA-CIEMAT). The sintering was performed in the temperature range of 1150–1300 °C. To optimise the sintering process, different heating rates (15, 30 and 60 °C/min) and dwell times (15, 30 and 60 min) were tested. For comparison, similar ferrite samples (with a toroid shape) were sintered in an electric furnace in the same temperature range using standard conditions (3.5 °C/min and 120 min at maximum temperature). The sintering time is considerably reduced by using the solar sintering and sintered samples present a microstructure that is more homogeneous and with less porosity. As a result, the sintered samples exhibit improved mechanical (elastic modulus, flexural strength and fracture toughness) and magnetic (initial magnetic permeability) properties.