Thermal expansion and thermal conductivity of (Ca_1-x,Mg_x)Zr₄(PO₄)₆ where x = 0.0-0.4

Solid-state reaction and sol-gel processing methods were used to prepare samples of (Ca_{1 - X,}Mg_X)Zr₄(PO₄)₆(CZP-CMZP) where x = 0.0-0.4. CMZP is a member of the NaZr₂(PO₄)₃ (NZP) class of ceramics and is being investigated for heat engine applications. Linear thermal expansion was determined with a dual push rod dilatometer and axial thermal expansion by high temperature X-ray diffraction and least squares refinement. Thermal diffusivity was determined with the laser flash method and specific heat by differential scanning calorimetry. Thermal conductivity was found by the product of the thermal diffusivity, specific heat, and bulk density of each sample. Results indicate that CMZP samples exhibit very low α̅_L values which become more positive as Mg²⁺ content is increased. Thermal expansion anisotropy (from room temperature to 1000°C) is significantly reduced by the addition of Mg²⁺. Samples where x = 0.4 exhibit the lowest anisotropy with α_a being essentially zero (hexagonal system). The thermal conductivity of CMZP samples is very low (0.56 W/m K at 200°C). Thermal conductivity values were observed to decrease with increasing Mg²⁺ content. The materials structure and cation site selection are discussed in relation to the observed properties.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Materials Engineering

Department dc:contributor.department

Materials Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1990

Author dc:creator

• Van Aken, Stephen Mark

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-04182009-041436

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/42159