Zirconia refractory—select the correct statement regarding its production and properties in high-temperature service.

Introduction / Context:
Zirconia (ZrO2) is a premium refractory used where extreme temperature, corrosion resistance, and thermal shock performance are required. Understanding its raw material sources and high-temperature behavior helps engineers choose it appropriately for slags and thermal barriers.

Given Data / Assumptions:

• ZrO2 can be derived from natural baddeleyite or synthesized from zircon (ZrSiO4) via decomposition.
• Zirconia shows excellent chemical stability toward many slags.
• Electrical properties vary with temperature and doping (stabilized zirconia can become an oxygen-ion conductor at high T).

Concept / Approach:
Baddeleyite is a natural form of ZrO2 and an industrial source of zirconia refractories. Chemically, zirconia exhibits high inertness and is often regarded as neutral, with good resistance to basic slags compared to acidic refractories. Electrically, while zirconia is an insulator at room temperature, stabilized zirconia can exhibit significant ionic conductivity at elevated temperatures. Therefore, absolute statements claiming it “cannot be used as an insulator” or that it remains a “perfect insulator” at high T are incorrect. Likewise, there is no requirement for water cooling in service; design relies on its inherent high-temperature stability.

Step-by-Step Solution:
Identify correct factual statement: production from baddeleyite.Evaluate slag resistance: zirconia is not known for reacting readily with basic slags; statement (a) is false.Assess electrical behavior: (c) is false because zirconia can act as an insulator at low/medium T; (d) is false because conductivity increases at high T (ionic conduction).Check practicality: (e) water cooling is not an inherent requirement.

Verification / Alternative check:
Raw materials and processing notes in refractory texts list baddeleyite as a source for ZrO2 bricks; property tables show temperature-dependent conductivity and broad chemical compatibility with basic slags, confirming the analysis.

Why Other Options Are Wrong:
(a) Misstates slag chemistry; zirconia is widely used in severe environments.(c) Overly absolute; zirconia is insulating at ambient conditions.(d) Overly absolute in the other direction; high-T ionic conduction occurs.(e) Not a standard operational requirement.

Common Pitfalls:
Assuming properties are temperature-independent; many ceramics show strong temperature dependence in electrical behavior and creep, requiring nuanced statements.

Final Answer:
It is commonly produced from the natural mineral baddeleyite.