Electrical resistivity comparison of refractory materials: which listed material exhibits the lowest electrical resistivity (i.e., highest electrical conductivity) at elevated temperature?

Introduction / Context:
Electrical resistivity is important when refractories interface with induction fields or electrical heating. Most oxide refractories are electrical insulators at room temperature, with resistivity decreasing as temperature rises. Carbon/graphite, however, behaves as a good electrical conductor across a wide temperature range.

Given Data / Assumptions:

• We compare typical engineering-grade materials: graphite versus common oxides (fireclay, alumina, zircon, silica).
• Temperature is elevated but below material degradation limits.
• We consider bulk behavior assuming dense shapes without unusual dopants.

Concept / Approach:
Graphite’s layered structure with delocalized electrons leads to high electrical conductivity (low resistivity). In contrast, silicate and oxide refractories have ionic/covalent bonding with large band gaps, making them electrical insulators at ambient temperatures; their resistivity drops with heat but remains far above that of graphite within normal service ranges. Therefore, among the listed options, graphite has the lowest resistivity.

Step-by-Step Solution:
Recognize graphite’s conductive nature.Recognize oxides as insulators with temperature-dependent conductivity.Select graphite as the lowest-resistivity material.

Verification / Alternative check:
Material property tables consistently report graphite resistivity orders of magnitude lower than alumina, silica, zircon, or fireclay compositions.

Why Other Options Are Wrong:
Fireclay / Alumina / Zircon / Silica: all are oxide-based and much more resistive than graphite, even at elevated temperatures.

Common Pitfalls:
Confusing thermal conductivity with electrical conductivity; graphite is high in both, but many oxides have low electrical conductivity despite variable thermal conductivity.

Final Answer:
Graphite