Dielectric loss of oxide single crystals and polycrystalline analogues from 10 to 320 K

The key factors influencing microwave dielectric loss are examined. A compa rison is made between single crystals and polycrystalline analogues. Measur ements of the temperature dependence of microwave dielectric losses in vari ous materials are reported, for temperatures between 20 and 300 K. Single c rystal and polycrystalline TiO2, LaAlO3, MgO and Al2O3 are considered. The temperature dependence of dielectric losses of certain single crystals (MgO and Al2O3) are found to be in good agreement with the theory of intrinsic losses for temperatures above 100 K. At lower temperatures losses due to de fects and grain boundaries dominate. The absolute value of the loss predict ed by theory is considerably lower than measured values. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.