Identify the non-oxide refractory: which of the following is not a single-oxide refractory material?

Introduction / Context:
Refractories are classified by chemistry into oxide, non-oxide, and carbonaceous groups. Single-oxide refractories are based on one dominant oxide (e.g., Al2O3, MgO, ZrO2). Non-oxide ceramics such as carbides, nitrides, and borides offer excellent high-temperature strength and thermal shock resistance but behave differently in oxidizing atmospheres.

Given Data / Assumptions:

• The question targets the chemical type, not brand names.
• We must choose the material that is not a single oxide.

Concept / Approach:
Zirconia (ZrO2) and magnesia (MgO) are classic single-oxide refractories. Silicon carbide (SiC) is a non-oxide ceramic compound and thus not a single oxide. Therefore, SiC is the correct choice.

Step-by-Step Solution:

Verification / Alternative check:
Handbooks group SiC with non-oxide refractories used for kiln furniture and crucibles, particularly where thermal shock is critical.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing “oxide content” with “single-oxide class”; overlooking that SiC oxidizes to SiO2 at high temperature in oxidizing atmospheres.

Final Answer:
Silicon carbide (SiC)