Ap. Cook et al., STUDY OF KBR PB(NO3)2 GROWTH AND CRYSTAL MORPHOLOGIES BY ACOUSTIC-EMISSION AND PHOTOMICROGRAPHIC TECHNIQUES/, Journal of crystal growth, 131(3-4), 1993, pp. 395-412
Simultaneous optical and acoustic information was used to elucidate th
e mechanism of acoustic emission (AE) generation during growth of pure
and Pb(NO3)2 doped KBr crystals. The mechanism of generation is postu
lated as one of inter-crystal interaction. The use of AE for monitorin
g the growth of different crystal structures was examined by studying
different KBr morphologies grown with varying degrees of Pb dopant (0-
32000 ppm). The AE profiles collected during the crystal growth of the
dendritic form of KBr (4080-8120 ppm Pb dopant), and the doped forms
of 12210 ppm Pb and above were found to give the best agreement with t
he image whitening profiles collected simultaneously. The dendritic fo
rm of KBr observed between 4080 and 8120 ppm consisted of finger-like
outgrowths, that spread outwards from the evaporating droplet. Scannin
g electron microscopy showed these fingers to consist of contiguous ch
ains of tiny (< 25 mum) octahedra, a microscopic structure that provid
ed many potential sources of emission. The total AE observed during th
e growth of the different KBr morphologies was found to vary in a repr
oducible manner over 60 experiments. The mass of crystals grown was le
ss than 0.12 g for all samples. Acoustic waveform analysis showed that
these signals arising during growth were distinguishable from artific
ially produced signals of bulk dendrite fracture and crystal impact.