Bulent Aktas

Microstructural and Mechanical Properties of Er2O3-ZrO2 Ceramics with Different Er2O3 Contents

Abstract In this study, the effect of erbium oxide (Er2O3) addition on the microstructure, sinterability and mechanical properties of cubic zirconia (c-ZrO2) was investigated. 0–15 wt% Er2O3 and c-ZrO2 powders were mixed by means of colloidal processing and the specimens were sintered at different temperatures for 1 hour. The XRD results showed the existence of cubic crystal structure in all specimens. The lattice parameter of the specimens decreased with increasing Er2O3 addition up to 10 wt% and remained unchanged after this amount. The grain size of the Er2O3 doped c-ZrO2 specimens dropped up to 5 wt% Er2O3 addition and stayed almost unchanged at higher Er2O3 contents. Both hardness and fracture toughness measurements were done using Vickers hardness tester. The fracture toughness values of the undoped, 1, 5, 10 and 15 wt% Er2O3 doped c-ZrO2specimens were found to be 1.64 MPam1/2, 1.77 MPam1/2, 2.06 MPam1/2, 2.57 MPam1/2 and 2.31 MPam1/2 respectively.

Microstructure, Mechanical and Electrical Properties of CuO Doped 8YSZ

Abstract The effect of the addition of a small amount of CuO on the microstructure, hardness, fracture toughness and electrical conductivity properties of 8YSZ were investigated using 8 mol% yttria-stabilized cubic zirconia (8YSZ). The addition of 1 wt% CuO to 8YSZ powders were doped using a colloidal process. Undoped and CuO doped 8YSZ specimens were pressureless sintered at 1400 °C for 10 h. The grain size measurement results showed that the presence of CuO as a intergranular second phase at the grain boundaries of the 8YSZ gave rise to a decrease in the grain size. The fracture toughness values for undoped and 1 wt% CuO-doped 8YSZ specimens were obtained as 1.79 and 2.20 MPa.m1/2, respectively. The decrease in the grain size of the 8YSZ with CuO addition caused an increase in the fracture toughness. The electrical conductivity of the undoped and 1 wt% CuO-doped 8YSZ specimens was measured using a frequency response analyzer in the frequency range of 100 mHz–13 MHz and at the temperature range of 300–800 °C. The electrical conductivity results showed that there was a decrease in the grain interior, and specific grain boundary conductivity, with the addition of a small amount of CuO to 8YSZ. The presence of a second phase layer with high resistance at the grain boundaries of the 8YSZ caused a decrease in the specific grain boundary conductivity.

Grain growth and sinterability in Er2O3-doped cubic zirconia (c-ZrO2)

Abstract The effects of the addition of Er2O3 on the grain growth and sinterability of c-ZrO2 were investigated using 8 mol.% yttria-stabilized cubic zirconia (c-ZrO2) and various amounts of Er2O3. For these purposes, the content of 0–15 wt.% Er2O3 and c-ZrO2 powders were doped using a colloidal process. Undoped and Er2O3-doped c-ZrO2 specimens were annealed for grain growth at different temperatures and holding times. An increase in annealing temperature and holding time caused grain growth in all specimens. Activation energy of the undoped c-ZrO2 obtained was 358 kJ mol−1 and the activation energies of 1, 5, 10 and 15 wt.% Er2O3-doped specimens obtained were 388, 403, 432 and 476 kJ mol−1, respectively. While excessive grain coarsening in the undoped c-ZrO2 was observed, a lesser level of grain growth occurred in the Er2O3-doped specimens, due to the segregation of Er2O3 at the grain boundaries and the restriction in the grain boundaries mobility of c-ZrO2.

Mechanical Properties of Soda-Lime-Silica Glasses with Variable Peanut Shell Contents

Mechanical Properties of Soda-Lime-Silica Glasses with Variable Peanut Shell

Influence of Co3O4 addition on the ionic conductivity and microstructural properties of yttria-stabilized zirconia (8YSZ)

Abstract In this study, 0 – 15 wt.% Co3O4 powders were added to 8 mol.% yttria-stabilized cubic zirconia (8YSZ) powders in order to determine the effect of Co3O4 addition and amount on the microstructure, sintering, and electrical properties of yttria-stabilized cubic zirconia. Colloidal processing was used to ensure uniform mixing of the powders and to obtain a homogeneous microstructure. X-ray diffraction results showed that the average lattice parameter of the yttria-stabilized cubic zirconia decreased from 5.146 Å to 5.135 Å upon Co3O4 addition, and that the lattice parameter did not change above a Co3O4 content of 1 wt.%. The initial decrease in the lattice parameter is attributable to the smaller ionic radius of Co3+ dissolved in the yttria-stabilized cubic zirconia matrix. The electrical conductivity of the specimens was measured using a frequency response analyzer in the range of 100 mHz – 13 MHz and 300 – 800 °C. Grain boundary conductivity of yttria-stabilized cubic zirconia was found to be enhanced with increasing Co3O4 addition, with the presence of electronically conductive cobalt oxide at grain boundary triple points increasing the grain boundary conductivity, due to an increase in the Co3+ and Co2+ electronic charge carrier ions.

Synthesis and mechanical properties of lanthanum oxide (La 2 O 3 )doped 8 mol % yttria-stabilized cubic zirconia (8YSZ)

In this study, 8 mol % yttria stabilized cubic zirconia (8YSZ) powders as a matrix material and 0-15 wt% La<inf>2</inf>O<inf>3</inf> powders as an additive were used in order to determine the effect of La<inf>2</inf>O<inf>3</inf> addition and amount on the phase stability, microstructure and mechanical properties of 8YSZ. XRD results showed the existence of cubic and hexagonal crystal structures for all addition amounts. Besides, La<inf>2</inf>O<inf>3</inf> up to 5 wt% was completely dissolved in the crystal structure of 8YSZ but, La<inf>2</inf>O<inf>3</inf> with higher than 5 wt% reacted with 8YSZ at high temperatures and formed pyrochloric La<inf>2</inf>Zr<inf>2</inf>O<inf>7</inf> compound. The hardness values of 8YSZ decreased and fracture toughness increased with the increase in La<inf>2</inf>O<inf>3</inf> amount.