Lutetium–yttrium oxyorthosilicate, also known as LYSO, is an inorganic chemical compound with main use as a

scintillator A scintillator ( ) is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the ab ...

crystal for

gamma radiation A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

detection. Its chemical formula is Lu_2(1-x)Y_2xSiO₅. The percentage of yttrium varies considerably, with values in the literature ranging from 5% to 70%. It is commonly used to build screens and electromagnetic

calorimeter A calorimeter is a device used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimeters ...

s in

particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

. LYSO crystals have the advantages of high light output and density, quick decay time, excellent energy resolution. The crystals are often grown in boules using the

Czochralski process The Czochralski method, also Czochralski technique or Czochralski process, is a method of crystal growth used to obtain single crystals (monocrystals) of semiconductors (e.g. silicon, germanium and gallium arsenide), metals (e.g. palladium, plati ...

, and cutting or polishing can be challenging because LYSO is brittle and hard.

Intrinsic radiation in gamma spectroscopy

LYSO scintillators contain naturally occurring ¹⁷⁶Lu, a radioactive isotope of lutetium that undergoes beta decay, emitting gamma radiation at 88 keV, 202 keV, and 307 keV. This intrinsic activity introduces background signals that can interfere with low-energy gamma detection, making LYSO less suitable for applications requiring ultra-low background noise. However, the intrinsic peaks can be used for energy calibration and gain stabilization, and advanced signal processing techniques—such as background subtraction, energy windowing, or coincidence timing discrimination—can help mitigate these effects, allowing LYSO to remain a viable choice for mid-to-high-energy gamma.

References

Crystals Lutetium compounds Phosphors and scintillators Silicates Yttrium compounds {{Inorganic-compound-stub