We investigated the dielectric loss tangent (tan δ) of sapphire single crystals produced by edge-defined film-fed growth (EFG) method using a dielectric resonator with YBa2Cu3Oy (YBCO) films. Surface resistance (Rs) of the YBCO film was low enough to obtain high resolution of tan δ measurement. For comparison, tan δ of the sapphire prepared by the Czochralsky (Cz) method was also evaluated. Measurements of 14 sapphire rods showed that EFG sapphire tends to have lower tan δ than Cz sapphire, while defects in Cz crystal were 1/14-1/2 less than that in EFG crystal. It means that the number of defects does not influence tan δ, if the density of defects is within the order of 104/cm2. In most EFG sapphire the value of tan δ at 30 K was estimated to be <1.0 × 10-7. It is usable for Rs measurement of high critical temperature superconducting materials.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering