PYROELECTRIC, DIELECTRIC, PIEZOELECTRIC, ELASTIC AND THERMOELASTIC PROPERTIES OF TRICLINIC LITHIUM HYDROGEN OXALATE MONOHYDRATE, LIHC2O4.H2O

Large single crystals of optical quality of triclinic lithium hydrogen oxalate monohydrate have been grown from aqueous solutions. Complete sets of pyroelectric, dielectric, piezoelectric, elastic and thermoelastic properties have been determined. The elastic constants were derived from ultrasonic measurements of resonance frequencies including piezoelectric coupling terms. These crystals possess strong pyroelectric and piezoelectric effects (coupling coefficient for thickness modes up to 0.52) which stem from the asymmetric hydrogen bond chains along [101]. These dominant bond chains are also responsible for the extremely large anisotropy of thermal expansion and elasticity. The crystals exhibit unusually large elastooptic effects in specific directions which in combination with the strong piezoelectric effects might be suitable for certain applications.