STRUCTURE AND HEAT-CAPACITY OF NA2O-2B2O3 GLASS - EFFECTS OF THE COOLING RATE

B-11-NMR magic angle spinning (MAS) and differential scanning calorime try (DSC) techniques have been used to study the effects of different cooling rates upon the structural and thermal properties of a glass of composition Na2O-2B2O3 (sodium pyroborate.). Samples obtained with co oling rates of 10(-2) and 10 K/s have been studied. While the short ra nge structure does not seem to be affected by the cooling rate, the th ermal analysis highlights some important differences, maybe located at medium range, between the heat capacities of fast and slow quenched s amples. An estimate of the length scale over which structural differen ces could be revealed by appropriate experiments is given.