DIELECTRIC-PROPERTIES OF HYDROTHERMALLY GROWN GALLIUM ORTHOPHOSPHATE SINGLE-CRYSTALS

GaPO4 single crystals of the low-temperature form were hydrothermally grown in 4M H3PO4 solution at 180 ° C. Single crystals 5.0×5.2×3.7mm3 in size could be grown in a silica glass vessel of 10 mm inner diameter. The dielectric properties of grown crystals were measured with the electric field parallel (E ∥c) and perpendicular (E ⊥c) to the c-axis. The values of dielectric constant (ie2800-01) of E ∥c and E ⊥c are about 10.3 and 7.8, respectively, at frequencies from 10 kHz to 1 MHz, and these are nearly independent of frequency at room temperature. However, these values increase with temperature in the temperature range about 310 to 500 K and in the frequency region below 1 MHz. Dielectric loss (ie2800-02) increases with increasing temperature at around 300 K (E ∥c) and 310 K (E ⊥c). From the log σ (conductivity) against 1/T plot in the intrinsic region at higher temperatures, the values of activation energy (E) for conduction are calculated to be about 0.17 and 0.33eV, for E ∥c and E ⊥c, respectively. © 1990 Chapman and Hall Ltd.