We report on the scintillation properties of Cs₂HfCl₆ (cesium hafnium chloride or CHC) as an example of a little-known class of non-hygroscopic compounds having the generic cubic crystal structure of K₂PtCl₆. The crystals are easily growable from the melt using the Bridgman method with minimal precursor treatments or purification. CHC scintillation is centered at 400 nm, with a principal decay time of 4.37 μs and a light yield of up to 54 000 photons/MeV when measured using a silicon CCD photodetector. The light yield is the highest ever reported for an undoped crystal, and CHC also exhibits excellent light yield nonproportionality. These desirable properties allowed us to build and test CHC gamma-ray spectrometers providing energy resolution of 3.3% at 662 keV.

Crystals of potassium lead bromide (KPB), a moisture-insensitive low-energy phonon laser host, were synthesized and purified. High-quality undoped and ${\mathrm{Tb}}^{3+}$ -doped (nominal doping concentration was $5\mathrm{mol}\%$ $\mathrm{Tb}{\mathrm{Br}}_3$ ) $\mathrm{K}{\mathrm{Pb}}_2{\mathrm{Br}}_5$ were grown by the vertical Bridgman technique. X-ray diffraction measurements indicated that, at room temperature, the material was monoclinic with space group $\mathrm{P}{2}_1∕\mathrm{c}$ , while at a high temperature the phase transformed to orthorhombic form. A reversible phase transition was observed around $256°\mathrm{C}$ upon the heating and cooling cycle from differential scanning calorimetric measurements. The material was found to be transparent in the broad range from $\sim 0.4\mu \mathrm{m}\text{to}25\mu \mathrm{m}$ and above. The transmission spectrum of a ${\mathrm{Tb}}^{3+}$ -doped crystal showed different absorption bands of ${\mathrm{Tb}}^{3+}$ at $4.5\mu \mathrm{m}$ , $3\mu \mathrm{m}$ , $2.3\mu \mathrm{m}$ , and $2\mu \mathrm{m}$ corresponding to ${}^{7}F_6–{}^{7}F_{\alpha }$ transitions, for $\alpha =2–5$ . The maximum phonon energy of undoped $\mathrm{K}{\mathrm{Pb}}_2{\mathrm{Br}}_5$ at room temperature was determined to be $134{\mathrm{cm}}^{-1}$ from Raman scattering spectrum.

Radiation detectors have been fabricated from Cd_1-xZn_xTe crystals and their performance has been studied with respect their Cd_1-xZn_xTe surface preparation. Energy resolution, leakage current, resistivity, ohmicity as well as surface roughness of the detectors were measured and compared for various chemical treatments. Etching in lactic acid has been found to lead to better ohmic contract, a rougher surface and higher leakage current. Bromine is effective in removing the damaged layer and when added to 20 percent lactic acid in ethylene glycol leads to a lower leakage current and consequently a better energy resolution. The best detector performance was obtained with a two step treatment consisting of a standard etchant (5 percent Br in methanol) followed by 2 percent Br in'20 percent lactic acid in ethylene glycol'. The results clearly demonstrate the important of surface chemical treatments in the fabrication of Cd_1-xZn_xTe radiation detectors.