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The beneficial effect of magnesium oxide upon the performance of crack-resistant oxide glasses has been explored in a series of aluminoborosilicate glasses with the compositions 60SiO2–(20 – x)­Al2O3–xB2O3–20Na2O and 60SiO2–(20 – x)­Al2O3–xB2O3–10Na2O–10MgO. The simultaneous presence of both boron and aluminum oxides in these glasses produces a synergetic effect upon crack resistance (CR), whose structural origins are being explored by detailed 11B, 23Na, 27Al, and 29Si single and double resonance solid-state NMR studies. Aluminum is exclusively four-coordinated, whereas boron is found in both three- and four-coordination. Substitution of B2O3 with Al2O3 and Na2O with MgO leads to a dramatic reduction of N 4, the fraction of four-coordinate boron, accompanied by an increase in CR. 11B/27Al double resonance NMR studies show only weak interactions between the boron oxide and aluminum oxide components, giving no evidence of the formation of new structural units not already realized in the ternary aluminosilicate and borosilicate glass systems. Rather, the effect of magnesium can be related to a dramatic reduction of the fraction of four-coordinate boron species compared to the analogous sodium-based system. This reduction results from a preference of the sodium ions to charge-compensate anionic AlO4/2 – species, combined with an unfavorable interaction of four-coordinate boron with Mg2+. Overall, the results give important insights into the Mg-driven structural network changes in this four-component glass system, providing a structural rationale for the dramatic effect of magnesium upon the mechanical properties of these glasses.

The effect of the average ionic potential ξ = Ze/r of the network modifier cations on crack initiation resistance (CR) and Young's modulus E has been measured for a series of alkaline‐earth aluminoborosilicate glasses with the compositions 60SiO2–10Al2O3–10B2O3–(20−x)M(2)O–xM’O (0 ≤ x ≤ 20; M, M’ = Mg, Ca, Sr, Ba, Na). Systematic trends indicating an increase of CR with increasing ionic potential, ξ, have been correlated with structural properties deduced from the NMR interaction parameters in 29Si, 27Al, 23Na, and 11B solid state NMR. 27Al NMR spectra indicate that the aluminum atoms in these glasses are essentially all four‐coordinated, however, the average quadrupolar coupling constant extracted from lineshape analysis increases linearly with increasing average ion potential computed from the cation composition. A similar linear correlation is observed for the average 29Si chemical shift, whereas the fraction of four‐coordinate boron decreases linearly with increasing ξ. Altogether the results indicate that in pure alkaline‐earth boroaluminosilicate glasses the crack resistance/E‐modulus trade‐off can be tailored by the alkaline‐earth oxide inventory. In contrast, the situation looks more complicated in glasses containing both Na2O and the alkaline‐earth oxides MgO, CaO, SrO, and BaO. For 60SiO2–10Al2O3–10B2O3–10MgO–10Na2O glass, the NMR parameters, interpreted in the context of their correlations with ionic potentials, are consistent with a partial network former role of the MgO component, enhancing crack resistance. Altogether the presence of MgO in aluminoborosilicate glasses helps overcome the trade‐off issue between high crack resistance and high elasticity modulus present in borosilicate glasses, thereby offering additional opportunities for the design of glasses that are both very rigid and very crack resistant.

Alkali-borosilicate glasses with composition (80-x)SiO2-xB2O3-20Na2O (10 ≤ x ≤ 30) were subjected to a 25 GPa compression and decompression at room temperature, resulting in density increases between 1.4% and 1.9%. The structural changes associated with this process have been investigated and compared with uncompressed glasses having the same thermal history. Systematic trends are identified, using Raman scattering and multinuclear solid-state Nuclear Magnetic Resonance (ssNMR). Perhaps counterintuitively, pressurization tends to increase the concentration of three-coordinated boron species (B(III) units) at the expense of four-coordinated boron (B(IV) units). 23Na NMR spectra show a systematic shift toward higher frequencies in the pressurized glasses, consistent with shorter average Na–O distances. The results are consistently explained in terms of a breakage of Si–O–B4 linkages resulting in the formation of nonbridging oxygen species. Pressure effects on the spectra are reversed by annealing the glasses at their respective glass transition temperatures.

Glass-ceramics have brought us necessary products for our modern society, such as heat-resistant tableware, biomaterials, electronics, photonics, and information technology. It has been more than 60 years since the invention of glass-ceramics, and even today, the research and development of characteristic glass-ceramics are ongoing. In particular, mechanical properties, thermal shock resistance, optical transparency, and ionic conductivity have always been important issues for glass researchers and the glass industry. This article reviews the fundamentals (materials and processes) and characteristic properties of modern glass-ceramics.