Oxide-based transparent polycrystalline ceramic materials

Principal investigators: Valentina Biasini, Laura Esposito, Jan Hostaša

Personnel involved: Andreana Piancastelli, Francesco Picelli, Rakesh Pandey

The activity is dedicated to the design and laboratory scale production of discs and slabs based on innovative polycrystalline and transparent ceramic oxides. Conditions for the transparency of a polycrystals are their optical isotropy and the absence of secondary phases, impurities, pores and scattering centers. All these aspects must be precisely controlled in order to avoid the formation of defects that would lead to the scattering of light and therefore to the decrease of transparency. Transparency is achieved through a careful design and control of the ceramic process until the complete elimination of residual porosity and secondary phases. The combination of purity and morphology of the raw materials and clean grain boundaries are required to accomplish the goal.

Due to the high melting temperature and good mechanical performance, transparent ceramics are suitable for high temperature applications in harsh and extreme environments, such as electromagnetic windows and ballistic applications, that cannot be provided by conventional transparent materials.

The transparent ceramics production process requires lower temperatures and shorter times than the growth of single crystals with the Czochralski method, and thus is economically advantageous, moreover, allowing large-scale production. Thanks to the variety of available shaping techniques, it also allows to obtain complex shapes and geometries without the need for expensive and time-consuming mechanical post-processing.

By the controlled addition of appropriate ions these materials can absorb, emit or transmit light at different wavelengths and can be used in solid-state lasers, IR windows, LEDs, in the detection of radiation and particles and for many applications in optics and photonics (detectors, scintillators, waveguides, light converters).

By varying the type and the quantities of the dopants, components with complex architectures, controlled dopants distributions, layered or coaxial, with a compositional gradient and/or mixed doping can be made.

For this purpose, different forming techniques can be used, like the tape casting of layers with different dopant contents followed by thermocompression and spray drying and pressing of powders.

The research group owns a consolidated know-how in the laboratory-scale production of:

  • YAG (Y3Al5O12) doped with rare earth ions (Yb, Nd, Cr, Ho, Er, Pr, etc.)
  • MgAl2O4 spinel for bulletproof windows
  • Lu2O3 and Sc2O3 doped with Yb3+

The sintering process is carried out in a clean high vacuum furnace and is followed by appropriate annealing cycles in air to promote the oxidation of the phases that were reduced by the vacuum cycle.

Instruments and Processes

Principal collaborations


  • CeMiLAP
  • CeMiLAP2
  • T-SC
  • bilateral project CNR ISTEC – HiLASE, CAS (Czech Republic)

Pubblications and patents

  • J. Hostaša, F. Picelli, S. Hříbalová, V. Nečina, Sintering aids, their role and behaviour in the production of transparent ceramics, Open Ceramics 7 (2021) 100137.
  • J. Hostaša, M. Schwentenwein, G. Toci, L. Esposito, D. Brouczek, A. Piancastelli, A. Pirri, B. Patrizi, M. Vannini, V. Biasini, Transparent laser ceramics by stereolithography, Scripta Materialia 187 (2020) 194-196.
  • G. Toci, J. Hostaša, B. Patrizi, V. Biasini, A. Pirri, A. Piancastelli, M. Vannini.: Fabrication and laser performances of Yb:Sc2O3 transparent ceramics from different combination of vacuum sintering and hot isostatic pressing conditions. Journal of the European Ceramic Society 40 (2020) 881-886.
  • J. Hostaša, F. Cova, A. Piancastelli, M. Fasoli, C. Zanelli, A. Vedda, V. Biasini.: Fabrication and luminescence of Ce-doped GGAG transparent ceramics, effect of sintering parameters and additives. Ceramics International 45 (2019) 23283-23288.
  • J. Hostaša, V. Nečina, T. Uhlířová, V. Biasini.: Effect of rare earth ions doping on the thermal properties of YAG transparent ceramics. Journal of the European Ceramic Society 39 (2019) 53-58.
  • A. Lapucci, M. Vannini, M. Ciofini, A. Pirri, M. Nikl, J. Li, L. Esposito, V. Biasini, J. Hostaša, T. Goto, G. Boulon, R. N. Maksimov, L. Gizzi, L. Labate, G. Toci.: Design and characterization of Yb and Nd doped transparent ceramics for high power laser applications: recent advancements. SPIE Proceedings 10254 (2017) 102540E-1.
  • J. Hostaša, A. Piancastelli, G. Toci, M. Vannini, V. Biasini.: Transparent layered YAG ceramics with structured Yb doping produced via tape casting. Optical Materials 65 (2017) 21-27.
  • J. Hostaša, V. Biasini, A. Piancastelli, M. Vannini, G. Toci.: Layered Yb:YAG ceramics produced by two different methods: processing, characterization, and comparison. Optical Engineering 55 (2016) 087104.
  • L. Esposito, A. Piancastelli, P. Miceli, S. Martelli.: A thermodynamic approach to obtaining transparent spinel (MgAl2O4) by hot pressing. Journal of the European Ceramic Society 35, 651-661 (2015).
  • L. Esposito, J. Hostaša, A. Piancastelli, G. Toci, D. Alderighi, M. Vannini, T. Epicier, A. Malchère, G. Alombert-Goget, G. Boulon.: Multilayered YAG-Yb:YAG ceramics: manufacture and laser performance. Journal of Materials Chemistry C 2 10138-10148 (2014).
  • W. Pabst, J. Hostaša, L. Esposito.: Porosity and pore size dependence of the real in-line transmission of YAG and alumina ceramics. Journal of the European Ceramic Society 34 2745-2756 (2014).
  • E. Cavalli, L. Esposito, J. Hostaša, M. Pedroni.: Synthesis and optical spectroscopy of transparent YAG ceramics activated with Er3+. Journal of the European Ceramic Society 33 1425-1434 (2013).
  • L. Esposito, A. Piancastelli, S. Martelli.: Production and characterization of transparent MgAl2O4 prepared by hot pressing. Journal of the European Ceramic Society 33, 737-747 (2013).
  • J. Hostaša, L. Esposito, D. Alderighi, A. Pirri.: Preparation and characterization of Yb-doped YAG ceramics. Optical Materials 35 798-803 (2013).
  • T. Epicier, G. Boulon, W. Zhao, M. Guzik, B. Jiang, A. Ikesue, L. Esposito.: Spatial distribution of the Yb3+ rare earth ions in Y3Al5O12 and Y2O3 optical ceramics as analyzed by TEM. Journal of Materials Chemistry 22, 18221-18229 (2012).