{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/108148"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/108148","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Chemical selection rules of single-phase high-entropy oxides","abstract":"High-entropy oxides, as a novel research field in ceramics, have been found to present state-of-the-art improvement in various properties. These contributions could be achieved by multiple cations homogeneously occupying the same polyhedral sites, introducing severe lattice distortion throughout a structure. However, the mechanism of chemical selection rules for designing new high-entropy oxides was still unclear. Randomly mixed, multi-components usually form composites instead of a single-phase, solid solution. In this research, twenty high-entropy lanthanide candidates were synthesized and examined to explore the function of two potential parameters: (1) cation size mismatch, and (2) preferred valence states. The oxide candidates were synthesized by the polymeric steric entrapment method to ensure homogeneous mixing among the cations. The evolution of phase transformation and structural stability from room temperature up to ~2000C were examined in a quadrupole lamp furnace and conical nozzle levitator at synchrotron X-ray facilities. The thermal expansion behaviors of single-phase, high-entropy, lanthanide oxides were measured. Cation size mismatch and preferred valence configurations have significant influences on the formation of high-entropy oxides. In most of circumstances, mixing cations with excess threshold in size mismatch (δ > 7) caused the formation of secondary phase(s), leading to failure in forming stable, single-phase, high-entropy oxides. By choosing cations with different preferences in valence configurations, the final structure could be constructed for a prototype with a similar combination of oxidation states. Furthermore, merging cations with different valence states could trigger phase transformations/separations during heat treatments. However, in high-entropy oxides, the contribution from configurational mixing entropy was thought to be negligible. Understanding the function of cation size mismatch and preferred valence configurations can benefit the ceramic community in the future when designing high-entropy oxides.","abstract_html":"High-entropy oxides, as a novel research field in ceramics, have been found to present state-of-the-art improvement in various properties. These contributions could be achieved by multiple cations homogeneously occupying the same polyhedral sites, introducing severe lattice distortion throughout a structure. However, the mechanism of chemical selection rules for designing new high-entropy oxides was still unclear. Randomly mixed, multi-components usually form composites instead of a single-phase, solid solution. In this research, twenty high-entropy lanthanide candidates were synthesized and examined to explore the function of two potential parameters: (1) cation size mismatch, and (2) preferred valence states. The oxide candidates were synthesized by the polymeric steric entrapment method to ensure homogeneous mixing among the cations. The evolution of phase transformation and structural stability from room temperature up to ~2000C were examined in a quadrupole lamp furnace and conical nozzle levitator at synchrotron X-ray facilities. The thermal expansion behaviors of single-phase, high-entropy, lanthanide oxides were measured. Cation size mismatch and preferred valence configurations have significant influences on the formation of high-entropy oxides. In most of circumstances, mixing cations with excess threshold in size mismatch (δ > 7) caused the formation of secondary phase(s), leading to failure in forming stable, single-phase, high-entropy oxides. By choosing cations with different preferences in valence configurations, the final structure could be constructed for a prototype with a similar combination of oxidation states. Furthermore, merging cations with different valence states could trigger phase transformations/separations during heat treatments. However, in high-entropy oxides, the contribution from configurational mixing entropy was thought to be negligible. Understanding the function of cation size mismatch and preferred valence configurations can benefit the ceramic community in the future when designing high-entropy oxides.","abstract_has_math":false,"creators":["Tseng, Kuo-Pin"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Materials Science & Engr","degree_department":null,"school":null,"contributors":["Kriven, Waltraud M","Zuo, Jian-Min","Shoemaker, Daniel P","Maaß, Robert"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-08-26T23:58:36Z","date_published":"2020-08-26T23:58:36Z","updated_at":"2026-07-22T22:24:47Z","subjects":["High entropy oxides","Phase transformations","Lanthanide oxides","Powder X-ray diffraction","High temperature","Size mismatch","Valence states","Thermal expansion"],"languages":["en"],"rights":["Copyright 2020 Kuo-Pin Tseng"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/108148","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Kriven, Waltraud M","Zuo, Jian-Min","Shoemaker, Daniel P","Maaß, Robert"]},{"key":"dc:creator","label":"Author","values":["Tseng, Kuo-Pin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-08-26T23:58:36Z","2022-08-26T23:58:55Z","2020-05-05","2020-05"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science & Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["High entropy oxides","Phase transformations","Lanthanide oxides","Powder X-ray diffraction","High temperature","Size mismatch","Valence states","Thermal expansion"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2020 Kuo-Pin Tseng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/108148"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["High-entropy oxides, as a novel research field in ceramics, have been found to present state-of-the-art improvement in various properties. These contributions could be achieved by multiple cations homogeneously occupying the same polyhedral sites, introducing severe lattice distortion throughout a structure. However, the mechanism of chemical selection rules for designing new high-entropy oxides was still unclear. Randomly mixed, multi-components usually form composites instead of a single-phase, solid solution. In this research, twenty high-entropy lanthanide candidates were synthesized and examined to explore the function of two potential parameters: (1) cation size mismatch, and (2) preferred valence states. The oxide candidates were synthesized by the polymeric steric entrapment method to ensure homogeneous mixing among the cations. The evolution of phase transformation and structural stability from room temperature up to ~2000C were examined in a quadrupole lamp furnace and conical nozzle levitator at synchrotron X-ray facilities. The thermal expansion behaviors of single-phase, high-entropy, lanthanide oxides were measured. Cation size mismatch and preferred valence configurations have significant influences on the formation of high-entropy oxides. In most of circumstances, mixing cations with excess threshold in size mismatch (δ > 7) caused the formation of secondary phase(s), leading to failure in forming stable, single-phase, high-entropy oxides. By choosing cations with different preferences in valence configurations, the final structure could be constructed for a prototype with a similar combination of oxidation states. Furthermore, merging cations with different valence states could trigger phase transformations/separations during heat treatments. However, in high-entropy oxides, the contribution from configurational mixing entropy was thought to be negligible. Understanding the function of cation size mismatch and preferred valence configurations can benefit the ceramic community in the future when designing high-entropy oxides.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-05-01","The student, Kuo-Pin Tseng, accepted the attached license on 2020-05-03 at 18:50.","The student, Kuo-Pin Tseng, submitted this Dissertation for approval on 2020-05-03 at 19:48.","This Dissertation was approved for publication on 2020-05-05 at 16:54.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15180 on 2020-08-25 at 17:29:32","Made available in DSpace on 2020-08-26T23:58:36Z (GMT). No. of bitstreams: 2 TSENG-DISSERTATION-2020.pdf: 13159359 bytes, checksum: 5c1713a8ce94e1d8c3bf313f2fc33e78 (MD5) LICENSE.txt: 4210 bytes, checksum: c5fdd3a1aba1dec6eacf88bfcdb3dea9 (MD5) Previous issue date: 2020-05-05","Embargo set by: Seth Robbins for item 115761 Lift date: 2022-08-26T23:58:55Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Chemical selection rules of single-phase high-entropy oxides"]}]}],"canonical_facts":{"dc:contributor":["Kriven, Waltraud M","Zuo, Jian-Min","Shoemaker, Daniel P","Maaß, Robert"],"dc:creator":["Tseng, Kuo-Pin"],"dc:date":["2020-08-26T23:58:36Z","2022-08-26T23:58:55Z","2020-05-05","2020-05"],"dc:description":["High-entropy oxides, as a novel research field in ceramics, have been found to present state-of-the-art improvement in various properties. These contributions could be achieved by multiple cations homogeneously occupying the same polyhedral sites, introducing severe lattice distortion throughout a structure. However, the mechanism of chemical selection rules for designing new high-entropy oxides was still unclear. Randomly mixed, multi-components usually form composites instead of a single-phase, solid solution. In this research, twenty high-entropy lanthanide candidates were synthesized and examined to explore the function of two potential parameters: (1) cation size mismatch, and (2) preferred valence states. The oxide candidates were synthesized by the polymeric steric entrapment method to ensure homogeneous mixing among the cations. The evolution of phase transformation and structural stability from room temperature up to ~2000C were examined in a quadrupole lamp furnace and conical nozzle levitator at synchrotron X-ray facilities. The thermal expansion behaviors of single-phase, high-entropy, lanthanide oxides were measured. Cation size mismatch and preferred valence configurations have significant influences on the formation of high-entropy oxides. In most of circumstances, mixing cations with excess threshold in size mismatch (δ > 7) caused the formation of secondary phase(s), leading to failure in forming stable, single-phase, high-entropy oxides. By choosing cations with different preferences in valence configurations, the final structure could be constructed for a prototype with a similar combination of oxidation states. Furthermore, merging cations with different valence states could trigger phase transformations/separations during heat treatments. However, in high-entropy oxides, the contribution from configurational mixing entropy was thought to be negligible. Understanding the function of cation size mismatch and preferred valence configurations can benefit the ceramic community in the future when designing high-entropy oxides.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-05-01","The student, Kuo-Pin Tseng, accepted the attached license on 2020-05-03 at 18:50.","The student, Kuo-Pin Tseng, submitted this Dissertation for approval on 2020-05-03 at 19:48.","This Dissertation was approved for publication on 2020-05-05 at 16:54.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15180 on 2020-08-25 at 17:29:32","Made available in DSpace on 2020-08-26T23:58:36Z (GMT). No. of bitstreams: 2 TSENG-DISSERTATION-2020.pdf: 13159359 bytes, checksum: 5c1713a8ce94e1d8c3bf313f2fc33e78 (MD5) LICENSE.txt: 4210 bytes, checksum: c5fdd3a1aba1dec6eacf88bfcdb3dea9 (MD5) Previous issue date: 2020-05-05","Embargo set by: Seth Robbins for item 115761 Lift date: 2022-08-26T23:58:55Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/108148"],"dc:language":["en"],"dc:rights":["Copyright 2020 Kuo-Pin Tseng"],"dc:subject":["High entropy oxides","Phase transformations","Lanthanide oxides","Powder X-ray diffraction","High temperature","Size mismatch","Valence states","Thermal expansion"],"dc:title":["Chemical selection rules of single-phase high-entropy oxides"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Materials Science & Engr"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:47Z"}