Piezoelectricity of poled silica containing thermal diffused tetravalent elements

We have previously reported piezoelectricity produced by poling in a germanium-doped silica(germanosilicate) glass film prepared by RF sputtering. However, we have not yet discussed the piezoelectricity of poled germanosillicate bulk samples. In this paper, we investigated piezoelectricity produced by poling in a germanium-doped glass substrate. The germanosilicate glass was prepared by doping germanium into silica glass substrates with thermodiffusion. The germanosilicate glass was poled by electric fields of 2-4 x 10(7) V/m at a temperature above 360-450 degreesC. Before the poling, no piezoelectric response was observed. After the poling, a piezoelectric response caused by normal stress T-33 on the film surface appeared. The maximum value of the piezoelectric constant d(33) of the poled substrate was larger than d(11) of quartz by about 5%. The same phenomenon was obserrved in titanium doped silica glass substrates.