title: Bismuth germanate as a perspective material for dielectric resonators in EPR spectroscopy.
abstract: High purity bismuth germanate (Bi4(GeO4)3, BGO) is proposed and implemented as an alternative material for dielectric EPR resonators. A significant improvement of the absolute sensitivity can be readily achieved by substituting the alumina insert (ring) by BGO-made one in commercially available X-band EPR probeheads. Four BGO dielectric inserts of 2, 3, 4 and 5mm inner diameter (ID) were made for comparison with standard 5mm inner diameter alumina insert. All inserts were introduced into commercial Bruker EPR resonator ER 4118X-MD-5W1, and their performance was investigated. The Q-values of empty resonators, B1 saturation curves and continuous wave EPR spectra of DPPH (2,2-diphenyl-1-picrylhydrazyl) were measured and analyzed in a temperature range 6-300K. BGO-made resonators were found superior in several important aspects. The background signals arising from BGO are much weaker compared to those of alumina at B=0-0.6T and T=6-300K; this is especially useful for measuring weak signals in the half-field region, as well as those near the central field. Moreover, mechanical properties of BGO allow easy fabrication of dielectric bodies having various shapes and sizes; in particular, small BGO resonators (e.g. ID=2 or 3mm) strongly enhance sensitivity for small samples due to increase of the filling factor. All these advantages have been also inspected in the pulse mode, proving that higher B1 fields and better filling factors can be achieved, contributing to the overall enhancement of the performance.
authors: International Tomography Center, SB RAS, Novosibirsk 630090, Russia; Novosibirsk State University, Novosibirsk 630090, Russia.
authors: Mikhail Y
authors: MY
authors: Ivanov
authors: Nikolaev Institute of Inorganic Chemistry, SB RAS, Novosibirsk 630090, Russia.
authors: Vladimir A
authors: VA
authors: Nadolinny
authors: Novosibirsk State University, Novosibirsk 630090, Russia; N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, Novosibirsk 630090, Russia.
authors: Elena G
authors: EG
authors: Bagryanskaya
authors: Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, Novosibirsk 630090, Russia.
authors: Yuriy A
authors: YA
authors: Grishin
authors: International Tomography Center, SB RAS, Novosibirsk 630090, Russia; Novosibirsk State University, Novosibirsk 630090, Russia.
authors: Matvey V
authors: MV
authors: Fedin
authors: International Tomography Center, SB RAS, Novosibirsk 630090, Russia; Novosibirsk State University, Novosibirsk 630090, Russia. Electronic address: sergey.veber@tomo.nsc.ru.
authors: Sergey L
authors: SL
authors: Veber
keywords: Bismuth germanate; Dielectric resonators; Electron paramagnetic resonance; Filling factor; Sensitivity enhancement