used and the same procedures as in example 1 were followed except the thermal treatment and sintering conditions as shown in table 1 the bending strengths of the sintered articles were also shown in table 1 shaped articles produced as in example 1 was thermally treated under the thermal treatment and sintering conditions indicated in table 2 in a nitrogen atmosphere under a pressure of 8 atms then the sintered articles were hip treated in a nitrogen atmosphere under a pressure of 2000 atms at a temperature of 1800 u00b0 c for one hour thirty test pieces each 3 mm u00d7 4 mm u00d7 40 mm were cut out from each obtained sintered and the bending strength according to jis r 1601 and the weibull modulus thereof were determined in order to determine a volume ratio of the columnar crystal particles of u03b2 si 3 n 4 in the sintered article one sectional surface of the sintered article was lap finished and etched with an etching solution of hf hno 3 2 1 at a temperature of 80 u00b0 c for 30 minutes then the sectional surface was observed by a scanning electron microscope at a magnification of 2500 and an area occupied by the columnar crystal particles.