Figure 4From: Morphology and electronic structure of nanoscale powders of calcium hydroxyapatite The presence of organic impurities in the samples according to IR spectroscopy. Annealing temperature samples: 1 - 200°C; 2 - 500°C; 3 - 900°C; 4 - 1,000°C. Transmission spectra were recorded in the absorption range in the 4,000 to 400 cm−1.Back to article page