Electroconductive thermal insulating material and infrared sensor

An infrared sensor comprising:

• a substrate;
• an infrared receiver;
• and
• an electroconductive thermal insulating material, wherein
• the electroconductive thermal insulating material comprises:
• first domains each having a phononic crystal, the phononic crystal having holes arranged in plan view;
• at least one second domain formed around the first domain in plan view and having no hole,
• a connected portion connected to at least one selected from the group consisting of the substrate and a member on the substrate;
• and
• a separated portion separated from the substrate, wherein
• the first domains are divided from each other by the second domain,
• in plan view, the first domain has a substantially polygonal shape in which at least one interior angle is greater than 90°,
• the infrared receiver is joined to the separated portion of the electroconductive thermal insulating material,
• the infrared receiver is supported by the electroconductive thermal insulating material in a state where the infrared receiver is separated from the substrate, and
• the electroconductive thermal insulating material includes, between a joined portion thereof joined to the infrared receiver and the connected portion, the first domain and the second domain.