STUDY OF KBR PB(NO3)2 GROWTH AND CRYSTAL MORPHOLOGIES BY ACOUSTIC-EMISSION AND PHOTOMICROGRAPHIC TECHNIQUES/

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.