Alkali ionic state behavior in γ-Irradiated borate glasses for medical ultrasonic transducer fabrication

Abstract

Lenses could be added to ultrasonic transducers used in medical applications to improve them. They may solve some limiting factors, like the acoustic impedance mismatch between the transducer and the tissues, the wave collimation difficulty, the wave scattering, etc. Novel ultrasonic transducers were developed that contained lenses made from new glass systems. Al2O3, MgO, and Li2O alkali-borate glass systems were prepared via the melt-quenching technique. Structural, electrical, and ultrasonic measurements were done with regard to the effect of gamma radiation. The XRD pattern showed the glassy, amorphous nature of the lenses. FTIR absorption spectra revealed the large stability of the main structural units of borate. Electron spin resonance (ESR) spectra clarified the low distortions caused by irradiation with g-values ∼ 2.025–2.026 and recognized the formation of oxygen hole centers (OHC) caused by breaking B–O connectivity. Al ions produced the most compact glass network, resulting in the highest ultrasonic velocity and wave passage. The characteristics of transducers with and without the lens were measured. The transducers with Al2O3 lenses demonstrated the lowest signal-to-noise ratio, the greatest beam diameter, and the highest sensitivity. The results ensured the effectiveness of the prepared glass as a lens in high-frequency ultrasonic transducers that are mainly used in medical applications.