Among the various inorganic matrices that might be suitable for obtaining transparent polycrystalline ceramics, tricalcium phosphate (TCP) caught our attention.
Indeed, TCP is an essential component of bone and teeth, and as its effective atomic number is close to that of the human bone, it could be one of the candidate for storage phosphors in dosimeters and can also be applied to scintillators for α-ray detection. We wish to activate this material with rare earth ions, in order to obtain optical transparent ceramics, which can be used as laser sources, scintillators and phosphors under UV and blue LED pumping.
We prepared transparent TCP ceramics by the Spark Plasma Sintering (SPS) technique, which is an efficient method to consolidate ceramics at low temperatures in a short time.
First, undoped translucent TCP ceramics were fabricated using optimized SPS parameters. Ceramics structure, microstructure and optical properties were investigated using X-ray diffraction, Scanning Electron Microscopy (SEM) and UV-Vis transmittance spectroscopy.
In a second step, the influence of LiF doping content on ceramics microstructure and transparency were studied in details using various sintering parameters such as: temperature, time of sintering and pressure. The density of the samples measured by the Archimedes method was ~3.13 g/cm³, which is equivalent to 99% of the theoretical density of Ca3(PO4)2.
For the microstructural analysis, the samples were prepared using ion polishing, this procedure enables to locate the tiny remaining pores. Optimized LiF content and SPS profile lead to dense ceramics having submicronic grain size (necessary to be reduce because of TCP birefringence) and promising transparency.