Electrooptical coefficients and temperature and pressure derivatives of the elastic constants of tetragonal Li₂B₄O₇

New values for the following properties of tetragonal Li 2 B 4 O 7 are reported: dielectric, electrostrictive, electrooptic, elastic, thermoelastic and piezoelastic constants, coefficients of thermal expansion and indices of refraction. These values are considered to be of superior precision compared to earlier published data. Most elastic constants possess positive temperature derivatives. This anomalous behaviour is not reflected in the pressure derivatives. The electrooptic effects are not large enough to compete with other materials used for technical applications.