  Research in ceramic scintillators has steadily progressed alongside the
research in bulk single crystal scintillator growth. As interest in faster
scintillation material production with lower cost increases, more research on
scintillating ceramics is needed. Research targeting optimization of optically
transparent ceramics that can rival bulk-grown crystals grown may lower cost,
increase yield, increase volume, and improve energy resolution in applications
and systems currently using sodium iodide and alike. Ceramic scintillators that
are dense (>5 g/cm3), have high effective Z (>60), are bright (>40,000
photons/MeV), and are not sensitive to moisture as well as those that can be
handled without protection are desired. Ultra-fast ceramic materials are also
of interest. This paper presents an equipment design and technique to produce
inorganic halide ceramic scintillators Cs2HfCl6 (CHC) and Tl2HfCl6 (THC).
Improvements and optimization of CHC and THC ceramic scintillator fabrication
are gauged by monitoring the energy resolution and peak position of 137Cs full
energy peak at 662 keV. With a 1-inch diameter CHC ceramic scintillator, energy
resolution of 5.4% (FWHM) and light yield of 20,700 ph/MeV are achieved, while
with a 16-mm diameter THC ceramic scintillator, energy resolution of 5.1%
(FWHM) and light yield of 27,800 ph/MeV are achieved. Decay times of 0.6
microseconds (21%) and 3.0 microseconds (79%) are measured for CHC and 0.3
microseconds (13%) and 1.0 microseconds (87%) for THC. Both ceramic CHC and THC
scintillators have similarly good proportionality data when compared to their
single crystal counterparts.
