Thermal expansion of bismuth triborate

Thermal expansion of the monoclinic nonlinear optical crystal BiB3O6 (bismu th triborate) was measured by dilatometry within the temperature range from 173 K to 573 K using single crystal samples of dimensions similar to7 x 7 x 8 mm(3). The four independent tenser coefficients are given and the calcu lated loci of zero thermal expansion of BiB3O6 are related to the loci of p hase matching for second harmonic generation. Characteristic features of th e crystal structure are taken to discuss the marked anisotropy of thermal e xpansion of BiB3O6.