It is a principal object of the present invention to provide low thermal expansion
materials able to answer to the needs of various uses. The present invention relates
to low thermal expansion materials constituted substantially from a crystalline
body represented by a compositional formula RM(QO4)3, wherein
R represents at least one selected from Zr and Hf, M represents at least one selected
from Mg, Ca, Sr, Ba and Ra, and Q represents at least one selected from W and Mo.
