Sintering of Negative and Zero Thermal Expansion Phases in A 2 M 3 O 12 Family: A Review

The unusual physical properties of ceramics in the A 2 M 3 O 12 family have been recognized for nearly three decades. Since then, numerous potential applications of A 2 M 3 O 12 ‐type ceramics have been proposed and examined. Several of these, particularly those involving components for thermal‐shock resistance or thermal shielding applications, require material in monolithic form. Such monoliths must meet stringent criteria, including theoretical densities of ≥99%, fine nanoscale to submicron microstructures, and strongly reduced microcracking. Achieving these outstanding features depends not only on the consolidation and sintering parameters but also on the properties of the precursor powders. Within this context, the present review provides a systematic overview of the synthesis methods used to produce precursor powders. The primary emphasis, however, is placed on sintering strategies, which are discussed in light of current knowledge. Both powder synthesis routes and consolidation/sintering approaches are examined in detail, with their respective advantages and limitations highlighted. Finally, the review outlines the current challenges and future perspectives in powder preparation and sintering of A 2 M 3 O 12 ‐type ceramics.