Introduction

During the past few decades, climate change has caused significant disruptions worldwide1. The alarming rate of the global temperature rise, exceeding 1.5 °C per decade, has led to severe consequences such as the melting of polar ice caps, rising sea levels, and extreme weather events2. To effectively tackle these challenges, it is crucial to switch to sustainable energy sources, utilize biocompatible and environmentally friendly materials, adopt green technologies, and reduce greenhouse gas emissions. International organizations focus on new technologies capable of reducing carbon footprint. Development of superconducting materials is an exceptional example3. Superconducting magnets and cables can be used for current storage and transmission without any carbon emissions4,5. The manufacture of rotors for superconducting electric motors6 or generators for aircraft7 and high-power wind generation systems8, as well as applications in the medical field, hold the highest priority9. The increasing demand for magnetic resonance imaging (MRI) requires production of high-performance magnets operated in higher temperatures10. Current MRI machines use magnet coils wound of conventional superconductors that need cooling by liquid helium (4 K). Superconductors such as MgB2 can operate at 20 K11 with more economical cooling via cryogen-free refrigerators12. The same advantage applies to Nuclear Magnetic Resonance (NMR) systems. In magnetic drug delivery (MDD), a sharp, uniform, and strong magnetic field is crucial, and a MgB₂ bulk can provide this more effectively than the recently proposed REBa2Cu3Oγ systems13. Recent research has indicated the potential to create large bulk superconducting magnets of MgB214,15,16. This material avoids the problem of weak links at grain boundaries, has negligible magnetic anisotropy, and features a simple stoichiometry. The possibility of large-scale synthesis at a relatively low cost and the ease of fabrication makes this superconductor suitable for various applications, particularly superconducting super magnets17,18,19.

Optimizing processing techniques, fine-tuning processing parameters, selecting the appropriate initial boron particle size, and carefully choosing dopants have significantly enhanced the critical current density (Jc) performance of bulk MgB₂ materials, as highlighted in recent reviews20,21. Tomoyuki et al. observed a notable improvement in Jc, particularly at high magnetic fields, by doping Ti at the Mg site and employing hot isostatic pressing (HIP) at 98 MPa and 900 °C for 3 h15. Similarly, Gharaibeh et al. reported that incorporating 2 wt% nano-CeO₂ into MgB₂ resulted in a significant Jc enhancement, reaching 780 kA cm–2 compared to the reference sample’s 395 kA cm–2 at 20 K and self-field22. Further advancements have been demonstrated using the infiltration and growth process, where MgB₂ samples doped with 10% B4C achieved the highest Jc of 440 kA/cm2 at 5 K17. In another study, a recent report indicated that tuning grain boundaries in sintered MgB2 through boron ultrasonication in 1-heptanol led to remarkable improvements in critical currents, reaching record values without any dopants—607 kA/cm2 at 10 K and 417 kA/cm2 at 20 K23. The application of the Spark Plasma Sintering (SPS) technique further improved bulk MgB2 density to 99%, resulting in a Jc of 2 × 105 A/cm2 in self-field24. Additionally, the combination of SPS with c-BN and C60 dopants introduced residual strains, ultimately boosting Jc to 0.9 × 106 A/cm2 in self-field at 5 K25. Grivel et al. reported a Jc of 600 kA cm–2 by adding Pt to Mg and synthesizing the material in an Ar-filled furnace using a two-step heating process: 700 °C for 1 h, followed by 800 °C for an additional hour26. Meanwhile, Batalu et al. employed SPS at 95 MPa and 1150 °C for 3 min using an ex-situ MgB2 precursor, achieving a Jc of 550 kA cm–2 at 20 K and 0 T27. To utilize MgB2 for commercial applications, further improvement of the critical current, Jc, is required. This can be accomplished by developing a nano-scale pinning structure allowing operation of bulk MgB2 at higher temperatures with high enough Jc. Achieving temporary goals, such as optimizing boron powder processing and synthesizing large, uniform bulks with high density, is crucial28. The primary strategy to improve performance involves microstructure manipulation23.

In this context, we have developed technology for fabricating high-performance compact MgB2 cryo-magnets with high trapped field values using a combination of spark plasma sintering (SPS) and carefully selected precursor materials. Additionally, using transmission electron microscopy, we observed a variety of nanoscale defects. These advancements underscore the potential of MgB2 as a transformative material in our pursuit of sustainable and efficient technologies to combat climate change.

SPS is a preferred method for producing highly dense MgB2 bulk superconductors29. The electric current flowing across the die containing the powder to sinter, together with the applied uniaxial pressure, serves as a heat source. The three main parameters—sintering temperature, dwell time, and applied pressure—control the speed of densification and granular growth. Compared to other sintering methods, SPS is unique in its ability to prepare dense samples while controlling grain growth and reducing processing time (usually 1–2 h)30. By utilizing the Spark Plasma Sintering (SPS) technique, compact and high-performance superconducting magnets can be fabricated. These magnets play a crucial role in various advanced applications, including magnetic shielding for sensitive laboratory instruments, superconducting magnetic energy storage systems, next-generation drug delivery, magnetic separation, maglev transportation, synchrotrons, and other high-energy physics experiments9. SPS is a key technology to unlock full potential of MgB2.

Trapped field (TF) in a bulk superconductor is directly proportional to Jc; thus, higher Jc values result in stronger TF17,19. To enhance Jc31, sintering temperature was optimized using the Mg-B phase diagram. During sintering, Mg melted and reacted with B, forming MgB2. The size and quality of the B- and other precursor powders play a crucial role in this process. We report here on incredible results achieved by applying spark plasma sintering technique on a mix of precursor powders consisting of a small quantity of fine silver, excess Mg, and carbon-coated nano boron. By means of Transmission Electron Microscopy (TEM), we discovered that these techniques led to the formation of a high nanoscale defect density in the MgB2 matrix. Consequently, in a compact bulk MgB2 sample measuring 20 mm in diameter and 5.5 mm thickness, we achieved a record-breaking critical current density, Jc, and trapped field of 4.21T at 11 K. Furthermore, a three-sample stack recorded a trapped field exceeding 5 T at 15 K, and when trapped field curve extrapolated to lower temperatures, it surpassed 6 T at 10 K. It is about half order of magnitude more than the best hard ferromagnets. These results are consistent with previous reports in the literature on larger samples15,17.

Experimental

To optimize the precursor composition, we varied precursor powders compositions, utilizing mechano-synthesis, solid state reactions, amorphous, crystalline, and nanoscopic boron, carbon encapsulated boron, silver, and excess Mg, applying SPS process onto the mixture. The search for the best precursor combination with the highest trapped field is demonstrated by the following four samples:

  1. 1.

    MgB2 (MgB2-1): [Mg (99.9%), 200 meshes; boron (99%), 300 meshes; 20 mm in diameter and 7.2 mm thick]

  2. 2.

    MgB2 (MgB2-2): [Mg (99.9%), 200 meshes; nano boron (98.5%), 200 nm; 20 mm in diameter and 5.8 mm thick]

  3. 3.

    MgB2 + 4wt% Ag (MgB2-3): [Mg (99.9%), 200 meshes; nano boron (98.5%), 200 nm; 4wt% metallic silver; 20 mm in diameter and 5.5 mm thick]

  4. 4.

    Mg1.075B2+4wt%Ag (MgB2-4): [Mg (99.9%), 200 meshes, 1.5% carbon encapsulated nano boron (98.5%), 200 nm, 4wt% metallic silver; 20 mm in diameter and 5.5 mm thick].

The best combination of initial composition and SPS process appeared to be the last one (MgB2-4).

High performance MgB2 sample production by SPS process

To create compact and high-performance superconducting cryo-magnets, an optimum combination of silver, carbon-coated boron, and excess magnesium was sintered by means of SPS. This technique involves hot pressing of the precursor powder mixed with uniaxial pressure and an electric current to sinter the powder (Fig. 1a). Three key parameters, sintering temperature, dwell time, and applied pressure, control the speed of densification and granular growth in SPS sintering. Compared to other methods, SPS allows us to produce dense samples while managing grain growth and reducing processing time.

A four-step in-situ reactive sintering was utilized with the aim of pre-synthesizing the MgB2 phase and avoiding magnesium evaporation. The samples were sintered in dynamic vacuum (10–3 bar). (i) compaction and pre-synthesis were carried out at 400 °C and 32 MPa for 20 min, (ii) synthesis was performed at 550 °C and 50 MPa for 20 min, (iii) sintering was done at 650 °C and 50 MPa for 20 min, and (iv) densification was accomplished at 900 °C and 86 MPa for 50 min. The obtained bulks were labelled as MgB2-1 to MgB2-4, depending on the precursor materials used and the addition of silver, excess Mg and carbon coated boron to the mixture (see above section). The samples were prepared using graphite dies coated with insulating boron nitride (BN) carbon foils.

For the magnetic measurements, small pieces measuring 1.5 × 1.5 ×  0.5 mm3 were cut from the sintered pellets. Magnetization hysteresis loops in fields ranging from − 1 to + 5 T were measured at temperatures between 10 K and 35 K using a commercial superconducting quantum interference device (SQUID Quantum Design—MPMS5). The Jc was estimated using the M-H loops and the extended Bean critical state model32,33,34:

$${J_c}=\frac{{20\Delta {\text{M}}}}{{\left( {{a^2}c\left( {b - \frac{a}{3}} \right)} \right)}}$$
(1)

In the extended Bean critical model, ∆M represents the change in magnetization hysteresis with respect to the change in the magnetic field. The equation includes a conversion factor that directly transforms ∆M from emu/cm3 to A/cm, eliminating the need for additional conversion. Here, a, and b denote the sample’s length and breadth, while c represents its thickness. The resulting Jc is expressed in A/cm2.

The MgB2-4 sample was prepared using the FIB and ion milling method for microstructural analysis, EDX, and elemental maps. To protect the surface, a carbon film and a tungsten film were deposited using a high-vacuum vapor deposition device in the FIB. A small piece of the sample was then extracted through FIB micro-sampling and subsequently thinned to a suitable thickness for TEM analysis. To further refine the sample and remove FIB-induced damage, Ar ion milling was performed. FIB processing was carried out at accelerating voltages of 40 kV, 30 kV, and 10 kV, while ion milling was conducted at 0.3 kV. The ion sources used were Ga for FIB and Ar for ion milling. Finally, the microstructural and EDX analyses of the MgB2-4 sample were performed using the JEOL Scanning Transmission Electron Microscope (JEM-F200 (HRP)), operating at an accelerating voltage of 200 kV with a beam diameter ranging from approximately 0.1–1.0 nm.

Results and discussion

Trapped field experiments

The process described above led to the creation of nano structural defects playing a crucial role in achieving high Jc and trapped field values in the MgB2 material. To determine the trapped field values using the field cooling (FC) method, we initially applied a magnetic field of 5–6 T, which is sufficient to achieve full magnetization parallel to the thickness direction of bulk MgB2 material at 50 K, above its superconducting transition temperature. This was done using a cryogen-free 10 T superconducting magnet (JMTD-10T100, Japan Superconductor Technology (JASTEC), Inc.). Subsequently, the bulk MgB2 was cooled down to 11 K, the lowest temperature of our apparatus. The applied magnetic field was then gradually reduced to 0 T at a rate of 22–220 mT/min. To ensure effective thermal contact, the bulk was placed on a thin indium sheet attached to the cold stage of a helium refrigerator.

The trapped field was measured using a cryogenic Hall sensor (BHT-921, F.W. Bell Inc.), positioned at the center of the bulk surface using GE7031 varnish. A Cernox thermometer, adhered beside the Hall sensor, monitored the bulk’s temperature. All samples had similar dimensions, with diameters of approximately 19–20 mm and thicknesses ranging from 5.5 to 7.2 mm. In the first experiment, we investigated the temperature dependence of the trapped field in an individual bulk MgB2 sample using the field cooling (FC) method. In the second experiment, the same FC method was applied to a triple-stacked arrangement of MgB2 bulks (MgB2-2, MgB2-3, and MgB2-4). A thin SUS plate (1 mm thick) was inserted between the bulks to create space for the cryogenic Hall probe with 0.7 mm in thickness.

Fig. 1
figure 1

Schematic representation of SPS device (a) and compact superconducting super-magnet produced by SPS process (b). The temperature dependence of the trapped magnetic field of the MgB2 material produced using various boron powders and initial composition (c).

Full size image

Figure 1c shows the trapped field of MgB2-1, MgB2-2, MgB2-3, and MgB2-4 bulks as a function of temperature, estimated between 40 K and 11 K. Normally, the trapped field (BT) value in MgB2 material produced using commercial boron powder is around 2.7 T at 15 K (MgB2-1). Utilization of nano boron in fabrication of the MgB2 material (MgB2-2) led to a remarkable improvement, reaching 3.3 T at 15 K, surpassing the value of the MgB2-1 reference by 23%. When carbon-coated nano boron was combined with an excess of Mg, 4wt% silver (MgB2-4), the trapped field value at 15 K rose to 3.76 T, exhibiting 40% enhancement over MgB2-1. At 11 K, the trapped field values of MgB2-1, MgB2-2, MgB2-3, and MgB2-4 were 3.1T, 3.70T, 4.03T, and 4.21T, respectively. Particularly interesting is the MgB2-4 sample, which achieved a trapped field of approximately 4.21 T at 11 K. With a diameter of 20 mm and a thickness of 5.5 mm (Fig. 1b), it represents one of the highest values reported to date for a bulk MgB2 material of this size and thickness.

Fig. 2
figure 2

(a) Shows the temperature dependence of the trapped magnetic field of the MgB2 material produced using various initial compositions, MgB2-2, MgB2-3, and MgB2-4, measured in the configuration shown in (b). (b) Displays how the bulks were magnetized by the external field Bex(t) and how the trapped field in the positions indicated in (b), BT(t), at T = 15 K developed in time. The trapped field values discussed in the text were achieved after 1500 min from reaching the highest value of the external magnetic field, Bex, (c). Magnetic field was detected by Hall probes positioned in the middle of 0.7 mm high gaps between two bulks as shown in (b).

Full size image

We note that magnetic field of any coil carrying electric current decays very fast with the distance from it, because of the stray fields spread from the single axial direction into a whole semi-space. In a superconducting bulk carrying superconducting current, it is the same. To reduce this effect, the MgB2 bulks were stacked into a stick (see Fig. 2b). In this way, the stray fields of each individual super-magnet combined with the stray fields of the neighbors and stood much more compact.

The superconductors’ stack was then magnetized at 15 K via field cooling (FC) in the static magnetic field of 6 T aligned with the magnet stack axis. After reducing the external field back to zero, the trapped field was measured by three probes, one lying on the single free surface (BT1) and two between two surfaces (BT2) and (BT3). The applied magnetic field was reduced to zero gradually, with a decreasing applied magnetic field rate, to prevent magnetic flux jumps: 6 T to 4.02 T at the rate of 10 mT/min, 4.02 T to 2.19 T at the rate of 5 mT/min, 2.19 T to 0.66 T at the rate of 3 mT/min, 0.66 T to 0.32 T at the rate of 2 mT/min, and 0.32 T to 0 T at the rate of 1 mT/min (see Fig. 2c).

Of particular significance were the two-sample stacks incorporating the MgB2-4 magnet. This specific configuration resulted in the trapped field exceeding 5 T, see Fig. 2a. The trapped field curve, when extrapolated to lower temperatures, surpassed 6 T at 10 K, indicating feasibility of compact super-magnets to form a 6 T class for various industrial applications. We observed similar results for double- and triple-stacked Ti-doped MgB₂ bulks with larger diameters of 28 mm and 40 mm and a thickness of approximately 10 mm and 20 mm35,36, where the trapped field between the bulks was dependent on the trapped field of each individual bulk. The difference between Bt2 and Bt3 (Bt2 < Bt3) in the stacked sample aligns with the Bt characteristics shown in Fig. 2a, where the Bt of MgB2-2 is lower than that of MgB2-3. Consequently, if the positions of MgB2-2 and MgB2-3 were exchanged in the stacked sample, Bt2 would be expected to exceed Bt3, a configuration that has been reported elsewhere32. Although we did not use multiple identical MgB2-4 bulks, they are expected to enhance the trapped field between the bulks due to their highest trapped field among our samples.

Earlier studies on bulk MgB2 super-magnets of 32 mm diameter, doped with B4C and produced using the infiltration growth (IG) process, demonstrated significant magnetic field trapping capabilities. In a two-sample stack configuration, the material trapped magnetic fields of 3.75 T at the center and 2.7 T at the top when measured at 5 K. Expanding this to a five-sample stack, a maximum trapped field of 4.15 T was observed between the centers of the second and third samples and 2.2 T at the top of the stack at 7.5 K16. When nanoscale precursor powders of Mg and B were used, the trapped fields were further enhanced, reaching 5.4 T at 12 K at the center of the bulk sample. Additionally, the temperature dependence of the trapped field in the shorter MgB2 sample exhibited a value of 3.2 T at 15 K18. Similarly, a cryo-magnet made of a 25 mm diameter disk-shaped bulk MgB2 achieved a maximum trapped field of 3 T at 17.5 K19. Additionally, 40 mm diameter disk-shaped bulk MgB2 doped with Ti and produced by hot isostatic pressing (HIP) displayed a trapped field of 3.45 T at 15 K15.

Critical current density (J c)

Trapped field is proportional to the critical current density and the MgB2 disk diameter. To assess critical currents of MgB2-1 and MgB2-4 samples, the magnetization loops were measured in the temperature range 7–35 K, and the critical current density was determined using the extended Bean critical state model32,33,34. The results of these measurements are presented in Fig. 3.

At 10 K and 20 K, the self-field Jc of the MgB2-4 sample reached the enormous values 1197 kA/cm2 and 857 kA/cm2, respectively. The MgB2-1 sample had the respective Jc values 320 kA/cm2 and 230 kA/cm2 (see Fig. 3a), nearly four times lower. At high magnetic field, 5 T, the MgB2-4 sample exhibited Jc of 104 A/cm2 at 10 K. The Jc values in the temperature range 20 to 35 K classify the material to be cooled to the operating temperature using liquid hydrogen or liquid neon. The self-field critical current density at 10 K, Jc =1197 kA/cm2, is the highest ever reported value (see Fig. 3b), indicating an extraordinary pinning strength attributed to the nanocrystalline MgB₂ grains and other defects. Additionally, the robust performance at high magnetic fields (Jc ~104 A/cm2 at 5 T) also points to strong pinning by point-like defects in the MgB2 matrix. The high Jc values in the entire temperature range 10–35 K and the accompanied trapped fields indicate excellence of the chosen chemical composition of precursors combined with the SPS process.

Fig. 3
figure 3

Variation of critical current density (Jc) with external magnetic field for (a) MgB2-1 and (b) MgB2-4 samples in the temperature range of 7–35 K.

Full size image
Fig. 4
figure 4

Pinning diagrams of the samples (a) MgB2-1 and (b) MgB2-4. We draw attention to the peak position in (b), close to b = 0.3, rarely seen in MgB2.

Full size image

Pinning diagram

The pining diagram represented by the f(b) dependence, where f is a normalized pinning force density, f = F/Fmax, and b is magnetic induction normalized with respect to irreversibility induction value, elucidates the prevailing type of the vortex pinning type. In Fig. 4, we can see the difference in pinning mechanism in the reference sample MgB2-1 (Fig. 4a) and the high-performance one, MgB2-4 (Fig. 4b). In the first case, the curve shape indicates at least two pinning types, one with the peak at or below b = 0.2, the second one, with the peak close to b = 0.3. According to Due Hughes model37, the f(b) observed at around b = 0.2 indicates pinning by grain boundaries and large particles, while the f(b) peak at b = 0.3 corresponds to point-like pins. With increasing temperature, the dominance between the two mechanisms in the MgB2-1 sample slightly changes, shifting from point-like defects at low temperatures towards grain boundary pinning at higher temperatures. It sounds quite logical; as vortex excitation grows with increasing temperature, large particles stay more effective in vortex pinning than small pins. In the MgB2-4 material, the pinning diagram consists of a single peak located close to b = 0.3, indicating a prevailing pinning by point-like pins and a reduced effect of grain boundaries.

The peak in MgB2-4 material is significantly more slender than in MgB2-1 and neither its width nor its position change with temperature. The pinning structure appears to be much more stable and uniform in MgB2-4 than in MgB2-1.

Microstructure

In Fig. 5a, a TEM image of the MgB2-4 material is displayed. When focusing on the grain interface and checking the lattice fringes at two adjacent crystal grains (see Fig. 5b), we find a high lattice matching. The continuous lattice fringes mean a high coherence and arrangement of atoms in the two adjacent grains.

Fig. 5
figure 5

TEM image of a grain boundary region in the MgB2-4 sample (a) and a close-up of its central section (b).

Full size image

Figure 6a presents a STEM dark-field (DF) image of a region without nanostrips, or strains shown in Fig. 5a. The image reveals spherical grains, ranging from 5 to 20 nm, dispersed throughout the MgB₂ matrix. Significantly, the nanoparticles, marked by white arrows, exhibit an optimal size for flux pinning, closely aligned to the superconducting coherence length38,39. These nanoparticles decorate areas acting as strong pinning centers, preventing motion of vortices. Thus, they enhance the material’s ability to sustain high critical currents.

Fig. 6
figure 6

STEM dark-field (DF) image of the MgB2-4 sample, showing nanometer-sized MgB₂O particles (marked by white arrows and labeled A1, A2, A3, A4, A5, and A6) (a). The other images are elemental maps of magnesium (b), boron (c), and oxygen (d).

Full size image
Table 1 Elemental analysis of a part of STEM image of the MgB2-4 sample using the EDX.
Full size table

To further investigate the composition of these nanoparticles, EDX analysis was performed with a beam diameter of approximately 1 nm to ensure accurate elemental measurements. The results, presented in Table 1, determine the composition of six nanoparticles with diameters ranging from 10 to 20 nm (A1, A2, A3, A4, A5 and A6). The analysis confirmed the presence of magnesium (Mg), boron (B), and oxygen (O) in these particles, with oxygen content varying across the MgB2 matrix (see Table 1).

Further insight into oxygen distribution was obtained from the elemental maps of magnesium (see Fig. 6b), boron (see Fig. 6c), and oxygen (see Fig. 6d), taken from the same region as shown in Fig. 6a. The maps for magnesium and boron exhibit a uniform contrast, indicating a consistent distribution of these elements throughout the sample. However, the oxygen map reveals distinct regions with higher oxygen content, correlating with the presence of MgB₂O nanoparticles. Although smaller particles (~ 5 nm) were not clearly resolved due to limited signal intensity, the larger MgB₂O particles contribute significantly to the enhanced flux pinning in MgB2 materials. These nanoparticles act as additional pinning centers, further anchoring magnetic vortices and improving the material’s performance at both low and high magnetic fields. We believe that just these particles are responsible for the shift of the normalized pinning force density from bpeak ≅0.2 towards 0.3 (see Fig. 4b) and thus enhancement of critical currents at high magnetic fields. The newly observed class of nanosized MgB2O particles in the MgB2 matrix, with dimensions close to the coherence length38,39, likely forms at grain boundaries or highly strained regions due to local oxidation. Silver appears to facilitate this process by affecting diffusion and the local chemical environment, while carbon-induced lattice strain promotes their formation, generates dislocations, and enhances particle development further40. Therefore, the bulk MgB2 preference was increased from normal boron (MgB2-1) to nano boron (MgB2-2), then to the addition of silver and nano boron (MgB2-3), and finally to a combination of silver, carbon-coated nano boron, and excess magnesium (MgB2-4).

Notably, MgB₂ typically exhibits a granular morphology, where grain boundaries serve as primary vortex pinning sites, particularly effective in low magnetic fields39. However, this pinning mechanism loses efficiency in high magnetic fields. In contrast, flux pinning by nanoscale particles is essential for supporting high critical current densities under intense magnetic conditions. Strong pinning centers, such as MgB₂O nanoparticles, effectively anchor magnetic vortices, inhibiting their motion and preserving superconductivity even in demanding environments.

All observed nano defects in the newly developed MgB2 material are significantly influenced by the synergistic effects of silver and carbon doping, excess magnesium, and the advanced spark plasma sintering process. These tailored defects play a pivotal role in enhancing the material’s properties, making it a game-changer for the development of compact cryo-magnets. Such magnets hold transformative potential across a range of industrial applications, including cutting-edge advancements in medical technology, space exploration, and power systems.

Summary

This study marks exceptional properties of the bulk MgB2 superconductor prepared by SPS at high pressure. At 10 K, we observed a record-breaking self-field critical current density of 1 MA/cm2 and an impressive, trapped field of 5 T at 15 K. These results can be attributed to the formation of a large variety of defects in the material. Notably, the MgB2 grains displayed a range of sizes, spanning from 50 to 200 nm. The best results were obtained on MgB2 prepared from Mg1.075B2+4wt%Ag (MgB2-4): [Mg (99.9%), 200 meshes, 1.5% carbon encapsulated nano boron (98.5%), 200 nm, 4wt% metallic silver] precursor mix processed by SPS technique. In contrast to most other MgB2 bulks, characterized by grain boundary pinning, pinning diagram of this compound pointed also to an important role of vortex pinning by point-like defects, with effectiveness and distribution independent of temperature. A strong interconnectivity among the grains was also observed, significantly enhancing the material’s performance in low magnetic fields. STEM combined with EDX and elemental mapping analysis revealed formation of a new class of nanometer-sized MgB2O particles within the MgB2 matrix, with sizes approaching the coherence length of the superconductor. These imaging techniques highlighted the occurrence of defects, which likely emerged during the SPS process applied on a material, using exceptionally appropriate precursors. These defects play a crucial role in achieving the record values in critical current density and trapped field in MgB2, reaching in a single bulk Jc ≅ 1.2 MA/cm2 and Bt = 6 T at 10 K and Jc = 1 MA/cm2 and Bt = 4.21 T at 11 K, and Bt = 6 T at 10 K in a triple-stacked bulk MgB2. These achievements represent a significant step forward in the area and cast an excellent promise for various industrial applications.