Crucibles and furnaces are two different components used in materials processing, especially in high-temperature applications. Here are the main differences between the two:

1. Function:
- Crucible: A crucible is a container designed to hold and heat materials at high temperatures. It is used to melt, cast or process materials such as metal, glass and ceramics.
- Furnace: A furnace is a device or structure used to heat materials to high temperatures. It provides a controlled environment for processes such as melting, annealing, heat treatment and chemical reactions.

2. Construction:
- Crucible: Typically made of materials such as graphite, clay, silicon carbide, or refractory metals such as tungsten, a crucible is a container that can withstand high temperatures and chemical reactions.
- Furnace: A furnace is a larger structure or piece of equipment that contains heating elements, insulation, and controls to achieve and maintain high temperatures. They can be designed for specific applications such as metal smelting, glass manufacturing or industrial heat treatment.

3. Application:
- Crucible: Mainly used to contain and process small to medium quantities of material at high temperatures, usually in localized areas.
- Furnace: used for heating and processing of materials on a large scale, usually involving continuous or intermittent operation. Furnaces are used in various industries for a variety of high-temperature processes.

In summary, while both crucibles and furnaces are used in high-temperature applications, a crucible is a container used to hold and process materials, while a furnace is a larger heating device or structure designed for industrial-scale heat processing.