Definition check: “Super refractories” are typically manufactured from very high-purity which class of compounds?

Introduction / Context:
“Super refractories” refer to refractory materials with exceptionally high refractoriness and chemical stability, often above 2000 °C, and engineered for severe service. Knowing their compositional classes helps in selecting materials for extreme environments like continuous casting hardware, high-temperature crucibles, or advanced kiln furniture.

Given Data / Assumptions:

• Super refractories are associated with very high purity and refractoriness.
• Representative examples include zirconia, thoria, and beryllia.
• The question asks for the general compound class, not an exhaustive list.

Concept / Approach:
High-purity oxides, particularly ZrO2, ThO2, and BeO, exhibit extremely high melting points, strong chemical inertness, and good high-temperature strength, making them prototypical “super refractory” materials. While carbides, borides, and nitrides also possess excellent high-temperature properties, the classic textbook definition of “super refractories” points first to these very pure oxides used in the most demanding thermal environments.

Step-by-Step Solution:
List classes: oxides, carbides, borides, nitrides.Recall canonical super-refractory examples: ZrO2, ThO2, BeO → oxides.Evaluate others: excellent materials but not the standard “super refractory” label in GK.Choose oxides as the correct class.

Verification / Alternative check:
Materials classification tables in ceramics texts consistently associate the term with very high-purity, ultra-high-melting oxides, confirming the selection.

Why Other Options Are Wrong:
Carbides/Borides/Nitrides: high-performance but not the classic definition emphasized by “super refractories.”Silicates: generally lower melting points compared with ultra-high-melting oxides.

Common Pitfalls:
Equating cutting-tool ceramics (often carbides/borides/nitrides) with the “super refractory” label used in furnace lining contexts.

Final Answer:
Oxides (e.g., ZrO2, ThO2, BeO)