Abstract: NZP materials because of its adjustable low thermal expansion has potential applications in the thermal shock, and NZP materials also has good chemical and thermal stability, also are frequently used as a ceramic radioactive element in waste package and fixed candidate materials.The NZP-type crystal structure allows a large number of ionic substitutions which leads to ceramics with adjustable thermal expansion properties or interesting ionic conductivity.However, NZP is difficult to fabricate into monoliths because it requires both high temperatures and long sintering times.An alternative low temperature route to obtain a tungsten(IV) and tin(IV) containing NZP crystalline phase uses a process of glass reactive sintering of a phosphate glass.Using a microwave oven, a glass with the appropriate composition in the NaPO3-Sn(II)O-W(VI)O3 ternary diagram is prepared by a conventional melting and casting technique.After crushing, the glass powder is pressed at room temperature.The green pellet is cured during various times at temperatures where glass reactive sintering takes place.DTA experiments, we have shown that different parameters influence the achievement of NZP phase.Consequently,specific conditions, such as initial glass composition,lass particle size lower than 100 μm, curing conducted under air, are required to obtain a glass-ceramic with a single crystalline phase with the NZP-type crystal structure.Sintering process requires the presence of aerobic, but the improvement of oxygen partial pressure of NZP phase content didn't make improvement.In addition, to strictly control the temperature higher than 710 ℃, guaranteed the NZP does not contain any phase of glass ceramic.

Key words: NZP materials because of its adjustable low thermal expansion has potential applications in the thermal shock, and NZP materials also has good chemical and thermal stability, also are frequently used as a ceramic radioactive element in waste package and fixed candidate materials.The NZP-type crystal structure allows a large number of ionic substitutions which leads to ceramics with adjustable thermal expansion properties or interesting ionic conductivity.However, NZP is difficult to fabricate into monoliths because it requires both high temperatures and long sintering times.An alternative low temperature route to obtain a tungsten(IV) and tin(IV) containing NZP crystalline phase uses a process of glass reactive sintering of a phosphate glass.Using a microwave oven, a glass with the appropriate composition in the NaPO3-Sn(II)O-W(VI)O3 ternary diagram is prepared by a conventional melting and casting technique.After crushing, the glass powder is pressed at room temperature.The green pellet is cured during various times at temperatures where glass reactive sintering takes place.DTA experiments, we have shown that different parameters influence the achievement of NZP phase.Consequently,specific conditions, such as initial glass composition,lass particle size lower than 100 μm, curing conducted under air, are required to obtain a glass-ceramic with a single crystalline phase with the NZP-type crystal structure.Sintering process requires the presence of aerobic, but the improvement of oxygen partial pressure of NZP phase content didn't make improvement.In addition, to strictly control the temperature higher than 710 ℃, guaranteed the NZP does not contain any phase of glass ceramic.