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• Vacuum and air sintered Bi-doped YIG have been prepared along with pure YIG using the sol–gel auto-combustion method. • The dielectric properties have enriched, and tangent loss has decreased for vacuum sintered Bi-doped YIG compared to YIG and air sintered Bi-doped YIG ceramics. • It also shows the better dielectric response with applied magnetic field so that it can be used for field sensing applications along with passive microwave devices. • We have observed large magneto-electric effect at the room temperature for all the ceramic samples and YBIG-V ceramic is maximum among them. • We have correlated the enhanced dielectric characteristics to the magnetic properties obtained through VSM measurements and attribute to the reduction in deficit oxygen states or Fe2+ concentration due to the vacuum sintering process which has also been confirmed through XPS studies. Yttrium iron garnet (YIG; Y 3 Fe 5 O 12) is an important material in the field of electronics because of its unique magnetic properties. This makes it ideal for use in devices such as microwave filters, amplifiers, sensors, and even magnetic storage devices. It is also used in spintronics, which is the study of the spin of electrons and how it can be manipulated for storage and computation. Additionally, it is highly stable and has low losses when exposed to electromagnetic fields, making it useful in applications such as controlling electric properties with magnetic fields or vice-versa, and magnetic resonance imaging (MRI). Herein, we have prepared YIG and Bi-doped YIG (Bi: YIG: Y 2 Bi 1 Fe 5 O 12) nanoparticles (NPs) using the sol–gel auto-combustion method. The obtained garnet powders were sintered at 950 °C both in an air and vacuum environment. We have explored the structural, electrical, optical, magnetic, and magneto-electric (ME) properties of Bi-doped YIG sintered in a vacuum (YBIG-V) and compared it with YIG and Bi-doped YIG sintered in the air (YBIG-A). We found the enhancement in dielectric response, magnetic properties, and the reduction in leakage current for the YBIG-V ceramics than for YBIG-A, YIG ceramics. We have studied the magneto-electric (ME) coupling at room temperature and found that YBIG-V ceramics show the better coupling strength with a maximum coupling coefficient, α ME of 354.3 mV/cm-Oe. The dielectric response of these samples significantly varies with the applied magnetic field, which will be positive in Bi-doped YIG ceramics and negative in pure YIG ceramics. Compared to YBIG-A, YBIG-V samples have better variation in dielectric response with the magnetic field, due to which they may be utilized for magnetic field sensing applications. We also observed that the resonance frequency varies with the applied magnetic field, which may be another parameter for field sensing applications. We attribute the enhancement of these properties in YBIG-V sample to the reduction in the average oxygen valency which is 1.63 for YBIG-A and 1.58 for YBIG-V. These values have been determined with the help of X-ray photoelectron emission spectroscopy data. [ABSTRACT FROM AUTHOR]