We have grown $$^{232}$$
232
Th:CaF$$_2$$
2
and $$^{229}$$
229
Th:CaF$$_2$$
2
single crystals for investigations on the VUV laser-accessible first nuclear excited state of $$^{229}$$
229
Th, with the aim of building a solid-state nuclear clock. To reach high doping concentrations despite the extreme scarcity (and radioactivity) of $$^{229}$$
229
Th, we have scaled down the crystal volume by a factor 100 compared to established commercial or scientific growth processes. We use the vertical gradient freeze method on 3.2 mm diameter seed single crystals with a 2 mm drilled pocket, filled with a co-precipitated CaF$$_2$$
2
:ThF$$_4$$
4
:PbF$$_2$$
2
powder in order to grow single crystals. Concentrations of $$4\cdot 10^{19}$$
4
·
10
19
cm$$^{-3}$$
-
3
have been realized with $$^{232}$$
232
Th with good (> 10%) VUV transmission. However, the intrinsic radioactivity of $$^{229}$$
229
Th drives radio-induced dissociation during growth and radiation damage after solidification. Both lead to a degradation of VUV transmission, currently limiting the $$^{229}$$
229
Th concentration to $$<5\times 10^{17}$$
<
5
×
10
17
cm$$^{-3}$$
-
3
.