(Wikipedia has a rule: If the inventor is alive he is a greedy SOB and we will not mention his invention)
HEAT RETENTIVE PLATES Also called InstaHot plate or Heat Storage Dish by the inventor, is a new type of ceramic plate designed to keep food hot at the table; Invented in El Paso TX, USA by Juan J. Ramirez around 2004. The inventor has been awarded the US Patent 7,176,426 published by the USPTO (United States Patent and Trademark Office) in 2007. It typically requires only one to 1.25 minutes preheating time in a microwave oven and remains hot typically for 1/2 hour (Still hot enough after that time that a bare hand can barely withstand the heat) while the rim remains cool for easy handling.
The inventor claims this is the first functional design change to a ceramic plate in thousands of years.
The working principle is based on the Stephan-Boltzmann law for radiation of hot bodies (Black body radiation principles) and a "new composition of material which is patent pending. See patent US 7,176,426 at USPTO website
The Inventor developed this invention as a result of a brain tumor operation and a stroke that impeded him from continuing his career in manufacturing, there is more information about "heat retentive plates" on the internet.