Ceramic and manufacturing method thereof, a heat emitter and the photovoltaic power generation syst

Provided is a ceramic which has high radiation intensity and enables heat emission having excellent wavelength selectivity. A ceramic which is mainly composed of a composition formula ARAlO4 (wherein A is Ca, Sr or Ba; and R is a rare earth element) or a composition formula ARGaO4 (wherein A is Ca, Sr or Ba; and R is a rare earth element), and which has pores at a porosity of from 20% to 40% (inclusive). The pores are connected with each other within the ceramic, but have portions that are not linearly continuous.